$ARGD
Argo Group International Holdings, Inc. Stock $argd

$argd Overview Financials Valuation SEC Filings Company Website

2020 Q3 Form 10-K Financial Statement

#000162828021004668 Filed on March 15, 2021

Income Statement

Concept	2020 Q3	2020 Q2	2020 Q1
Revenue	$481.8M	$452.7M	$434.4M
YoY Change	-1.15%	-7.35%	-14.72%
Cost Of Revenue
YoY Change
Gross Profit
YoY Change
Gross Profit Margin
Selling, General & Admin
YoY Change
% of Gross Profit
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$10.60M	$9.100M	$5.000M
YoY Change	60.61%	28.17%	-25.37%
% of Gross Profit
Operating Expenses	$494.5M	$438.1M	$451.4M
YoY Change	-2.6%	-3.71%	12.88%
Operating Profit
YoY Change
Interest Expense	$6.900M	$7.000M	$7.800M
YoY Change	-10.39%	-25.53%	-9.3%
% of Operating Profit
Other Income/Expense, Net
YoY Change
Pretax Income	-$26.50M	$5.900M	-$25.70M
YoY Change	-2.21%	-78.78%	-125.32%
Income Tax	-$3.400M	$11.30M	-$1.000M
% Of Pretax Income		191.53%
Net Earnings	-$23.10M	-$5.400M	-$24.70M
YoY Change	-11.15%	-120.0%	-128.2%
Net Earnings / Revenue	-4.79%	-1.19%	-5.69%
Basic Earnings Per Share	-$0.72	-$0.16	-$0.72
Diluted Earnings Per Share	-$0.72	-$0.16	-$0.72
COMMON SHARES
Basic Shares Outstanding	34.67M shares	34.63M shares	34.47M shares
Diluted Shares Outstanding	34.67M shares	34.63M shares	34.47M shares

Balance Sheet

Concept	2020 Q3	2020 Q2	2020 Q1
SHORT-TERM ASSETS
Cash & Short-Term Investments
YoY Change
Cash & Equivalents	$300.4M	$187.7M	$158.7M
Short-Term Investments
Other Short-Term Assets
YoY Change
Inventory
Prepaid Expenses
Receivables
Other Receivables
Total Short-Term Assets	$11.00M
YoY Change
LONG-TERM ASSETS
Property, Plant & Equipment	$84.00M	$87.00M	$89.00M
YoY Change	-22.94%	-23.01%	-22.61%
Goodwill	$156.5M	$156.5M	$161.4M
YoY Change	-11.58%	-11.58%	-8.81%
Intangibles	$90.80M	$91.10M	$91.50M
YoY Change	-1.52%	-1.62%	-1.72%
Long-Term Investments	$5.006B	$4.852B	$4.811B
YoY Change	-2.36%	-0.53%	-1.9%
Other Assets	$30.00M	$32.00M	$60.00M
YoY Change
Total Long-Term Assets	$10.71B
YoY Change
TOTAL ASSETS
Total Short-Term Assets	$11.00M
Total Long-Term Assets	$10.71B
Total Assets	$10.72B	$10.38B	$10.18B
YoY Change	2.75%	2.22%	2.36%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable
YoY Change
Accrued Expenses	$301.0M	$254.0M	$287.0M
YoY Change	-25.5%	-37.28%	-23.87%
Deferred Revenue
YoY Change
Short-Term Debt	$0.00	$0.00	$0.00
YoY Change
Long-Term Debt Due
YoY Change
Total Short-Term Liabilities	$301.0M	$281.0M	$305.0M
YoY Change	-25.5%	-30.62%	-19.1%
LONG-TERM LIABILITIES
Long-Term Debt	$457.0M	$579.0M	$578.0M
YoY Change	-21.07%	0.0%	-0.34%
Other Long-Term Liabilities
YoY Change
Total Long-Term Liabilities	$457.0M	$579.0M	$578.0M
YoY Change	-21.07%	0.0%	-0.34%
TOTAL LIABILITIES
Total Short-Term Liabilities	$301.0M	$281.0M	$305.0M
Total Long-Term Liabilities	$457.0M	$579.0M	$578.0M
Total Liabilities	$8.873B	$8.671B	$8.564B
YoY Change	3.67%	5.21%	6.03%
SHAREHOLDERS EQUITY
Retained Earnings	$698.4M	$734.4M	$750.4M
YoY Change	-23.0%	-22.1%	-19.11%
Common Stock	$1.425B	$1.423B	$1.420B
YoY Change	0.4%	0.51%	-0.01%
Preferred Stock
YoY Change
Treasury Stock (at cost)	$455.1M	$455.1M	$455.1M
YoY Change	0.0%	0.0%	0.0%
Treasury Stock Shares	11.32M shares	11.32M shares	11.32M shares
Shareholders Equity	$1.849B	$1.708B	$1.614B
YoY Change
Total Liabilities & Shareholders Equity	$10.72B	$10.38B	$10.18B
YoY Change	2.75%	2.22%	2.36%

Cashflow Statement

Concept	2020 Q3	2020 Q2	2020 Q1
OPERATING ACTIVITIES
Net Income	-$23.10M	-$5.400M	-$24.70M
YoY Change	-11.15%	-120.0%	-128.2%
Depreciation, Depletion And Amortization	$10.60M	$9.100M	$5.000M
YoY Change	60.61%	28.17%	-25.37%
Cash From Operating Activities	$204.5M	-$71.70M	-$31.40M
YoY Change	1.94%	18.51%	-156.47%
INVESTING ACTIVITIES
Capital Expenditures	-$8.200M	-$5.300M	$2.300M
YoY Change	13.89%	-36.9%	-68.49%
Acquisitions
YoY Change
Other Investing Activities	-$86.90M	$119.8M	$2.800M
YoY Change	-60.91%	8.51%	-86.07%
Cash From Investing Activities	-$95.10M	$114.5M	$61.30M
YoY Change	-58.56%	12.25%	-293.38%
FINANCING ACTIVITIES
Cash Dividend Paid	$10.90M	$10.60M	$10.70M
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	6.500M	-9.900M	-$10.40M
YoY Change	-165.66%	-12.39%	-0.95%
NET CHANGE
Cash From Operating Activities	204.5M	-71.70M	-$31.40M
Cash From Investing Activities	-95.10M	114.5M	$61.30M
Cash From Financing Activities	6.500M	-9.900M	-$10.40M
Net Change In Cash	115.9M	32.90M	$20.90M
YoY Change	-398.71%	8.94%	54.81%
FREE CASH FLOW
Cash From Operating Activities	$204.5M	-$71.70M	-$31.40M
Capital Expenditures	-$8.200M	-$5.300M	$2.300M
Free Cash Flow	$212.7M	-$66.40M	-$33.70M
YoY Change	2.36%	27.45%	-169.77%

Facts In Submission

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CY2020	us-gaap	Net Income Loss NetIncomeLoss	-54100000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	-14100000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	57000000.0	USD
CY2020	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	4600000	USD
CY2019	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	0	USD
CY2018	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	0	USD
CY2020	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	-58700000	USD
CY2019	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	-14100000	USD
CY2018	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	57000000.0	USD
CY2020	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	-1.70
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	-0.41
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.68
CY2020	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	-1.70
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	-0.41
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.65
CY2020	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.24
CY2019	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.24
CY2018	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.08
CY2020	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	34614813	shares
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	34205954	shares
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	33922009	shares
CY2020	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	34614813	shares
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	34205954	shares
CY2018	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	34678781	shares
CY2020	us-gaap	Debt And Equity Securities Gain Loss Excluding Other Than Temporary Impairment Loss DebtAndEquitySecuritiesGainLossExcludingOtherThanTemporaryImpairmentLoss	-7200000	USD
CY2019	us-gaap	Debt And Equity Securities Gain Loss Excluding Other Than Temporary Impairment Loss DebtAndEquitySecuritiesGainLossExcludingOtherThanTemporaryImpairmentLoss	100400000	USD
CY2018	us-gaap	Debt And Equity Securities Gain Loss Excluding Other Than Temporary Impairment Loss DebtAndEquitySecuritiesGainLossExcludingOtherThanTemporaryImpairmentLoss	-64400000	USD
CY2020	argo	Other Than Temporary Impairment Losses Fixed Maturities OtherThanTemporaryImpairmentLossesFixedMaturities	0	USD
CY2019	argo	Other Than Temporary Impairment Losses Fixed Maturities OtherThanTemporaryImpairmentLossesFixedMaturities	20300000	USD
CY2018	argo	Other Than Temporary Impairment Losses Fixed Maturities OtherThanTemporaryImpairmentLossesFixedMaturities	6600000	USD
CY2020	argo	Other Than Temporary Impairment Losses Other Invested Assets OtherThanTemporaryImpairmentLossesOtherInvestedAssets	0	USD
CY2019	argo	Other Than Temporary Impairment Losses Other Invested Assets OtherThanTemporaryImpairmentLossesOtherInvestedAssets	0	USD
CY2018	argo	Other Than Temporary Impairment Losses Other Invested Assets OtherThanTemporaryImpairmentLossesOtherInvestedAssets	1000000.0	USD
CY2020	us-gaap	Other Than Temporary Impairment Loss Debt Securities Portion Recognized In Earnings OtherThanTemporaryImpairmentLossDebtSecuritiesPortionRecognizedInEarnings	0	USD
CY2019	us-gaap	Other Than Temporary Impairment Loss Debt Securities Portion Recognized In Earnings OtherThanTemporaryImpairmentLossDebtSecuritiesPortionRecognizedInEarnings	20300000	USD
CY2018	us-gaap	Other Than Temporary Impairment Loss Debt Securities Portion Recognized In Earnings OtherThanTemporaryImpairmentLossDebtSecuritiesPortionRecognizedInEarnings	7600000	USD
CY2020	us-gaap	Gain Loss On Investments GainLossOnInvestments	-7200000	USD
CY2019	us-gaap	Gain Loss On Investments GainLossOnInvestments	80100000	USD
CY2018	us-gaap	Gain Loss On Investments GainLossOnInvestments	-72000000.0	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	-54100000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	-14100000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	57000000.0	USD
CY2020	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Before Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentBeforeTax	-15300000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Before Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentBeforeTax	-200000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Before Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentBeforeTax	-3400000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax	600000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax	1800000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax	-1200000	USD
CY2020	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	95200000	USD
CY2019	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	88000000.0	USD
CY2018	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	-93900000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	12800000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	-9900000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	-5400000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	66500000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	95900000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	-90700000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	100000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	400000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	-200000	USD
CY2020	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	16500000	USD
CY2019	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	14200000	USD
CY2018	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	-13500000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	0	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	-1200000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	-500000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	16400000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	15000000.0	USD
CY2018	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	-12800000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	50100000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	80900000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-77900000	USD
CY2020	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	-4000000.0	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	66800000	USD
CY2018	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	-20900000	USD
CY2017Q4	us-gaap	Stockholders Equity StockholdersEquity	1812900000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	57000000.0	USD
CY2018	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	-75500000	USD
CY2018	us-gaap	Other Comprehensive Income Other Net Of Tax OtherComprehensiveIncomeOtherNetOfTax	-2400000	USD
CY2018	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	530882	shares
CY2018	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	59.83
CY2018	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	31700000	USD
CY2018	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	15900000	USD
CY2018	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	7400000	USD
CY2018	us-gaap	Stock Issued During Period Value Employee Stock Purchase Plan StockIssuedDuringPeriodValueEmployeeStockPurchasePlan	2000000.0	USD
CY2018Q4	argo	Common Stock Dividend Rate Percentage CommonStockDividendRatePercentage	0.15
CY2018	us-gaap	Stock Issued During Period Value Stock Dividend StockIssuedDuringPeriodValueStockDividend	0	USD
CY2018	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.08
CY2018	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	37500000	USD
CY2018	us-gaap	Tax Cuts And Jobs Act Of2017 Reclassification From Aoci To Retained Earnings Tax Effect TaxCutsAndJobsActOf2017ReclassificationFromAociToRetainedEarningsTaxEffect	0	USD
CY2018Q4	us-gaap	Stockholders Equity StockholdersEquity	1735000000.0	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	-14100000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	82500000	USD
CY2019	us-gaap	Other Comprehensive Income Other Net Of Tax OtherComprehensiveIncomeOtherNetOfTax	-1600000	USD
CY2019	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	16300000	USD
CY2019	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	13800000	USD
CY2019	us-gaap	Stock Issued During Period Value Employee Stock Purchase Plan StockIssuedDuringPeriodValueEmployeeStockPurchasePlan	2500000	USD
CY2019	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.24
CY2019	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	43100000	USD
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	1763700000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	-54100000	USD
CY2020	us-gaap	Stock Issued During Period Value New Issues StockIssuedDuringPeriodValueNewIssues	144000000.0	USD
CY2020	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	65900000	USD
CY2020	us-gaap	Other Comprehensive Income Other Net Of Tax OtherComprehensiveIncomeOtherNetOfTax	-15800000	USD
CY2020	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	8100000	USD
CY2020	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	6700000	USD
CY2020	us-gaap	Stock Issued During Period Value Employee Stock Purchase Plan StockIssuedDuringPeriodValueEmployeeStockPurchasePlan	2500000	USD
CY2020	us-gaap	Dividends Preferred Stock Cash DividendsPreferredStockCash	4600000	USD
CY2020	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.24
CY2020	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	43000000.0	USD
CY2020Q4	us-gaap	Stockholders Equity StockholdersEquity	1857800000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	-54100000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	-14100000	USD
CY2019	us-gaap	Depreciation And Amortization DepreciationAndAmortization	27300000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	57000000.0	USD
CY2020	us-gaap	Depreciation And Amortization DepreciationAndAmortization	33200000	USD
CY2018	us-gaap	Depreciation And Amortization DepreciationAndAmortization	31900000	USD
CY2020	us-gaap	Share Based Compensation ShareBasedCompensation	8700000	USD
CY2019	us-gaap	Share Based Compensation ShareBasedCompensation	16900000	USD
CY2018	us-gaap	Share Based Compensation ShareBasedCompensation	18300000	USD
CY2020	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-21600000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-23500000	USD
CY2018	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-21400000	USD
CY2020	us-gaap	Gain Loss On Investments GainLossOnInvestments	-7200000	USD
CY2019	us-gaap	Gain Loss On Investments GainLossOnInvestments	80100000	USD
CY2018	us-gaap	Gain Loss On Investments GainLossOnInvestments	-72000000.0	USD
CY2020	argo	Undistributed Earnings From Alternative Investment Portfolio UndistributedEarningsFromAlternativeInvestmentPortfolio	-8600000	USD
CY2019	argo	Undistributed Earnings From Alternative Investment Portfolio UndistributedEarningsFromAlternativeInvestmentPortfolio	-19900000	USD
CY2018	argo	Undistributed Earnings From Alternative Investment Portfolio UndistributedEarningsFromAlternativeInvestmentPortfolio	-19000000.0	USD
CY2020	us-gaap	Gain Loss On Disposition Of Assets1 GainLossOnDispositionOfAssets1	-1900000	USD
CY2019	us-gaap	Gain Loss On Disposition Of Assets1 GainLossOnDispositionOfAssets1	-7200000	USD
CY2018	us-gaap	Gain Loss On Disposition Of Assets1 GainLossOnDispositionOfAssets1	-300000	USD
CY2020	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	USD
CY2019	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	15600000	USD
CY2018	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	USD
CY2020	us-gaap	Increase Decrease In Accrued Interest Receivable Net IncreaseDecreaseInAccruedInterestReceivableNet	-3900000	USD
CY2019	us-gaap	Increase Decrease In Accrued Interest Receivable Net IncreaseDecreaseInAccruedInterestReceivableNet	-1500000	USD
CY2018	us-gaap	Increase Decrease In Accrued Interest Receivable Net IncreaseDecreaseInAccruedInterestReceivableNet	3500000	USD
CY2020	us-gaap	Increase Decrease In Premiums Receivable IncreaseDecreaseInPremiumsReceivable	-84800000	USD
CY2019	us-gaap	Increase Decrease In Premiums Receivable IncreaseDecreaseInPremiumsReceivable	455100000	USD
CY2018	us-gaap	Increase Decrease In Premiums Receivable IncreaseDecreaseInPremiumsReceivable	558300000	USD
CY2020	us-gaap	Increase Decrease In Deferred Policy Acquisition Costs IncreaseDecreaseInDeferredPolicyAcquisitionCosts	4600000	USD
CY2019	us-gaap	Increase Decrease In Deferred Policy Acquisition Costs IncreaseDecreaseInDeferredPolicyAcquisitionCosts	-7000000.0	USD
CY2018	us-gaap	Increase Decrease In Deferred Policy Acquisition Costs IncreaseDecreaseInDeferredPolicyAcquisitionCosts	7300000	USD
CY2020	us-gaap	Increase Decrease In Prepaid Reinsurance Premiums IncreaseDecreaseInPrepaidReinsurancePremiums	33200000	USD
CY2019	us-gaap	Increase Decrease In Prepaid Reinsurance Premiums IncreaseDecreaseInPrepaidReinsurancePremiums	87800000	USD
CY2018	us-gaap	Increase Decrease In Prepaid Reinsurance Premiums IncreaseDecreaseInPrepaidReinsurancePremiums	47600000	USD
CY2020	us-gaap	Increase Decrease In Future Policy Benefit Reserves IncreaseDecreaseInFuturePolicyBenefitReserves	280200000	USD
CY2019	us-gaap	Increase Decrease In Future Policy Benefit Reserves IncreaseDecreaseInFuturePolicyBenefitReserves	509000000.0	USD
CY2018	us-gaap	Increase Decrease In Future Policy Benefit Reserves IncreaseDecreaseInFuturePolicyBenefitReserves	338300000	USD
CY2020	us-gaap	Increase Decrease In Unearned Premiums IncreaseDecreaseInUnearnedPremiums	63700000	USD
CY2019	us-gaap	Increase Decrease In Unearned Premiums IncreaseDecreaseInUnearnedPremiums	111700000	USD
CY2018	us-gaap	Increase Decrease In Unearned Premiums IncreaseDecreaseInUnearnedPremiums	76400000	USD
CY2020	argo	Increase Decrease In Reinsurance Payables And Funds Held IncreaseDecreaseInReinsurancePayablesAndFundsHeld	-238200000	USD
CY2019	argo	Increase Decrease In Reinsurance Payables And Funds Held IncreaseDecreaseInReinsurancePayablesAndFundsHeld	243300000	USD
CY2018	argo	Increase Decrease In Reinsurance Payables And Funds Held IncreaseDecreaseInReinsurancePayablesAndFundsHeld	232000000.0	USD
CY2020	us-gaap	Increase Decrease In Accrued Income Taxes Payable IncreaseDecreaseInAccruedIncomeTaxesPayable	-17500000	USD
CY2019	us-gaap	Increase Decrease In Accrued Income Taxes Payable IncreaseDecreaseInAccruedIncomeTaxesPayable	11400000	USD
CY2018	us-gaap	Increase Decrease In Accrued Income Taxes Payable IncreaseDecreaseInAccruedIncomeTaxesPayable	3300000	USD
CY2020	argo	Increase Decrease In Accrued Underwriting Expenses IncreaseDecreaseInAccruedUnderwritingExpenses	-43700000	USD
CY2019	argo	Increase Decrease In Accrued Underwriting Expenses IncreaseDecreaseInAccruedUnderwritingExpenses	-10600000	USD
CY2020	us-gaap	Proceeds From Sale Of Other Investments ProceedsFromSaleOfOtherInvestments	103900000	USD
CY2018	argo	Increase Decrease In Accrued Underwriting Expenses IncreaseDecreaseInAccruedUnderwritingExpenses	111600000	USD
CY2020	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	-9800000	USD
CY2019	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	77000000.0	USD
CY2018	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	-17800000	USD
CY2020	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	71900000	USD
CY2019	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	182800000	USD
CY2018	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	301800000	USD
CY2020	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	1080000000.0	USD
CY2019	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	1394300000	USD
CY2018	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	1259100000	USD
CY2020	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	569800000	USD
CY2019	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	522200000	USD
CY2018	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	418600000	USD
CY2020	argo	Proceedsfrom Sale And Maturity Of Equity Securities Fvni ProceedsfromSaleAndMaturityOfEquitySecuritiesFVNI	25400000	USD
CY2019	argo	Proceedsfrom Sale And Maturity Of Equity Securities Fvni ProceedsfromSaleAndMaturityOfEquitySecuritiesFVNI	374700000	USD
CY2018	argo	Proceedsfrom Sale And Maturity Of Equity Securities Fvni ProceedsfromSaleAndMaturityOfEquitySecuritiesFVNI	238900000	USD
CY2019	us-gaap	Proceeds From Sale Of Other Investments ProceedsFromSaleOfOtherInvestments	83100000	USD
CY2018	us-gaap	Proceeds From Sale Of Other Investments ProceedsFromSaleOfOtherInvestments	101800000	USD
CY2020	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	2038100000	USD
CY2019	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	1859100000	USD
CY2018	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	1936000000.0	USD
CY2020	argo	Payments To Acquire Equity Securities Fvni PaymentsToAcquireEquitySecuritiesFVNI	78900000	USD
CY2019	argo	Payments To Acquire Equity Securities Fvni PaymentsToAcquireEquitySecuritiesFVNI	61200000	USD
CY2018	argo	Payments To Acquire Equity Securities Fvni PaymentsToAcquireEquitySecuritiesFVNI	170500000	USD
CY2020	us-gaap	Payments To Acquire Other Investments PaymentsToAcquireOtherInvestments	35500000	USD
CY2019	us-gaap	Payments To Acquire Other Investments PaymentsToAcquireOtherInvestments	63700000	USD
CY2018	us-gaap	Payments To Acquire Other Investments PaymentsToAcquireOtherInvestments	42600000	USD
CY2020	argo	Payments For Proceeds From Change In Foreign Regulatory Deposits And Voluntary Pools PaymentsForProceedsFromChangeInForeignRegulatoryDepositsAndVoluntaryPools	5400000	USD
CY2019	argo	Payments For Proceeds From Change In Foreign Regulatory Deposits And Voluntary Pools PaymentsForProceedsFromChangeInForeignRegulatoryDepositsAndVoluntaryPools	0	USD
CY2018	argo	Payments For Proceeds From Change In Foreign Regulatory Deposits And Voluntary Pools PaymentsForProceedsFromChangeInForeignRegulatoryDepositsAndVoluntaryPools	-13000000.0	USD
CY2020	us-gaap	Payments For Proceeds From Short Term Investments PaymentsForProceedsFromShortTermInvestments	-285400000	USD
CY2019	us-gaap	Payments For Proceeds From Short Term Investments PaymentsForProceedsFromShortTermInvestments	490400000	USD
CY2018	us-gaap	Payments For Proceeds From Short Term Investments PaymentsForProceedsFromShortTermInvestments	132200000	USD
CY2020	argo	Increase Decrease In Settlements Of Foreign Currency Exchange Forward Contracts IncreaseDecreaseInSettlementsOfForeignCurrencyExchangeForwardContracts	9400000	USD
CY2019	argo	Increase Decrease In Settlements Of Foreign Currency Exchange Forward Contracts IncreaseDecreaseInSettlementsOfForeignCurrencyExchangeForwardContracts	300000	USD
CY2018	argo	Increase Decrease In Settlements Of Foreign Currency Exchange Forward Contracts IncreaseDecreaseInSettlementsOfForeignCurrencyExchangeForwardContracts	-1500000	USD
CY2020	us-gaap	Proceeds From Divestiture Of Businesses Net Of Cash Divested ProceedsFromDivestitureOfBusinessesNetOfCashDivested	28300000	USD
CY2019	us-gaap	Proceeds From Divestiture Of Businesses Net Of Cash Divested ProceedsFromDivestitureOfBusinessesNetOfCashDivested	0	USD
CY2018	us-gaap	Proceeds From Divestiture Of Businesses Net Of Cash Divested ProceedsFromDivestitureOfBusinessesNetOfCashDivested	0	USD
CY2020	us-gaap	Proceeds From Sale Of Productive Assets ProceedsFromSaleOfProductiveAssets	38000000.0	USD
CY2019	us-gaap	Proceeds From Sale Of Productive Assets ProceedsFromSaleOfProductiveAssets	0	USD
CY2018	us-gaap	Proceeds From Sale Of Productive Assets ProceedsFromSaleOfProductiveAssets	0	USD
CY2020	us-gaap	Cash Acquired From Acquisition CashAcquiredFromAcquisition	0	USD
CY2019	us-gaap	Cash Acquired From Acquisition CashAcquiredFromAcquisition	0	USD
CY2018	us-gaap	Cash Acquired From Acquisition CashAcquiredFromAcquisition	15600000	USD
CY2020	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	20200000	USD
CY2019	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	29900000	USD
CY2018	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	32200000	USD
CY2020	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-13600000	USD
CY2019	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	13100000	USD
CY2018	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	300000	USD
CY2020	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-24300000	USD
CY2019	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-142800000	USD
CY2018	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-268300000	USD
CY2020	us-gaap	Repayments Of Notes Payable RepaymentsOfNotesPayable	125000000.0	USD
CY2019	us-gaap	Repayments Of Notes Payable RepaymentsOfNotesPayable	600000	USD
CY2018	us-gaap	Repayments Of Notes Payable RepaymentsOfNotesPayable	0	USD
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CY2019	us-gaap	Proceeds From Issuance Of Preferred Stock And Preference Stock ProceedsFromIssuanceOfPreferredStockAndPreferenceStock	0	USD
CY2018	us-gaap	Proceeds From Issuance Of Preferred Stock And Preference Stock ProceedsFromIssuanceOfPreferredStockAndPreferenceStock	0	USD
CY2020	us-gaap	Proceeds From Issuance Of Shares Under Incentive And Share Based Compensation Plans ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlans	1800000	USD
CY2019	us-gaap	Proceeds From Issuance Of Shares Under Incentive And Share Based Compensation Plans ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlans	1900000	USD
CY2018	us-gaap	Proceeds From Issuance Of Shares Under Incentive And Share Based Compensation Plans ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlans	1600000	USD
CY2020	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	0	USD
CY2019	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	0	USD
CY2018	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	31700000	USD
CY2020	us-gaap	Payments Of Dividends Preferred Stock And Preference Stock PaymentsOfDividendsPreferredStockAndPreferenceStock	4600000	USD
CY2019	us-gaap	Payments Of Dividends Preferred Stock And Preference Stock PaymentsOfDividendsPreferredStockAndPreferenceStock	0	USD
CY2018	us-gaap	Payments Of Dividends Preferred Stock And Preference Stock PaymentsOfDividendsPreferredStockAndPreferenceStock	0	USD
CY2020	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	43000000.0	USD
CY2019	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	43100000	USD
CY2018	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	37500000	USD
CY2020	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-26800000	USD
CY2019	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-41800000	USD
CY2018	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-67600000	USD
CY2020	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	-9800000	USD
CY2019	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	-100000	USD
CY2018	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	-2800000	USD
CY2020	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	11000000.0	USD
CY2019	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-1900000	USD
CY2018	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-36900000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	137800000	USD
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	139700000	USD
CY2017Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	176600000	USD
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	148800000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	137800000	USD
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	139700000	USD
CY2020	us-gaap	Number Of Reportable Segments NumberOfReportableSegments	2	segment
CY2020	us-gaap	Contracts In Force Subject To Participation Through Reinsurance Percentage ContractsInForceSubjectToParticipationThroughReinsurancePercentage	1
CY2020	argo	Number Of Statutory Trust NumberOfStatutoryTrust	11	trust
CY2020	argo	Number Of Charitable Foundation NumberOfCharitableFoundation	1	foundation
CY2020	us-gaap	Malpractice Loss Contingency Return Of Premiums MalpracticeLossContingencyReturnOfPremiums	6500000	USD
CY2019	us-gaap	Malpractice Loss Contingency Return Of Premiums MalpracticeLossContingencyReturnOfPremiums	5400000	USD
CY2020	argo	Malpractice Loss Contingency Premiums Receivables Due MalpracticeLossContingencyPremiumsReceivablesDue	200000	USD
CY2019	argo	Malpractice Loss Contingency Premiums Receivables Due MalpracticeLossContingencyPremiumsReceivablesDue	300000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Accumulated Amortization FiniteLivedIntangibleAssetsAccumulatedAmortization	51700000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Gross FiniteLivedIntangibleAssetsGross	147300000	USD
CY2020Q4	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	15600000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Gross FiniteLivedIntangibleAssetsGross	112200000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Accumulated Amortization FiniteLivedIntangibleAssetsAccumulatedAmortization	55500000	USD
CY2020	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	1100000	USD
CY2019	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	1700000	USD
CY2018	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	3300000	USD
CY2020Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	163300000	USD
CY2019Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	153200000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	130400000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	140400000	USD
CY2020	us-gaap	Depreciation Depreciation	24100000	USD
CY2019	us-gaap	Depreciation Depreciation	24400000	USD
CY2018	us-gaap	Depreciation Depreciation	24500000	USD
CY2019	argo	Number Of Properties Held For Sale NumberOfPropertiesHeldForSale	4	property
CY2020	argo	Numberof Properties Sold NumberofPropertiesSold	2	property
CY2020Q4	us-gaap	Accumulated Other Comprehensive Income Loss Foreign Currency Translation Adjustment Net Of Tax AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax	37900000	USD
CY2019Q4	us-gaap	Accumulated Other Comprehensive Income Loss Foreign Currency Translation Adjustment Net Of Tax AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax	-22600000	USD
CY2020	us-gaap	Interest Paid Net InterestPaidNet	26400000	USD
CY2019	us-gaap	Interest Paid Net InterestPaidNet	33100000	USD
CY2018	us-gaap	Interest Paid Net InterestPaidNet	31300000	USD
CY2020	us-gaap	Income Taxes Paid IncomeTaxesPaid	47700000	USD
CY2019	us-gaap	Income Taxes Paid IncomeTaxesPaid	24000000.0	USD
CY2018	us-gaap	Income Taxes Paid IncomeTaxesPaid	0	USD
CY2020	us-gaap	Proceeds From Income Tax Refunds ProceedsFromIncomeTaxRefunds	1800000	USD
CY2019	us-gaap	Proceeds From Income Tax Refunds ProceedsFromIncomeTaxRefunds	100000	USD
CY2018	us-gaap	Proceeds From Income Tax Refunds ProceedsFromIncomeTaxRefunds	-24800000	USD
CY2020	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	45900000	USD
CY2019	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	23900000	USD
CY2018	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	24800000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	3629900000	USD
CY2019Q4	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	136000000.0	USD
CY2019Q4	us-gaap	Other Investments OtherInvestments	486600000	USD
CY2019Q4	us-gaap	Investments Investments	5097500000	USD
CY2019Q4	us-gaap	Premiums Receivable At Carrying Value PremiumsReceivableAtCarryingValue	676500000	USD
CY2019Q4	us-gaap	Reinsurance Recoverables On Paid And Unpaid Losses ReinsuranceRecoverablesOnPaidAndUnpaidLosses	3107200000	USD
CY2019Q4	us-gaap	Deferred Income Tax Assets Net DeferredIncomeTaxAssetsNet	10600000	USD
CY2019Q4	us-gaap	Other Assets OtherAssets	387900000	USD
CY2019Q4	us-gaap	Assets Assets	10508800000	USD
CY2019Q4	argo	Accrued Underwriting Expenses And Other Liabilities AccruedUnderwritingExpensesAndOtherLiabilities	221900000	USD
CY2019Q4	us-gaap	Reinsurance Payable ReinsurancePayable	1201200000	USD
CY2019Q4	us-gaap	Policyholder Contract Deposits PolicyholderContractDeposits	55200000	USD
CY2019Q4	us-gaap	Accrued Income Taxes AccruedIncomeTaxes	13900000	USD
CY2019Q4	us-gaap	Liabilities Liabilities	8745100000	USD
CY2019Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	793700000	USD
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	1763700000	USD
CY2019Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	10508800000	USD
CY2019Q4	us-gaap	Premiums Earned Net PremiumsEarnedNet	425800000	USD
CY2019	us-gaap	Premiums Earned Net PremiumsEarnedNet	1729700000	USD
CY2019Q4	us-gaap	Gain Loss On Investments GainLossOnInvestments	21800000	USD
CY2019	us-gaap	Gain Loss On Investments GainLossOnInvestments	80100000	USD
CY2019Q4	us-gaap	Revenues Revenues	484600000	USD
CY2019	us-gaap	Revenues Revenues	1970000000.0	USD
CY2019Q4	argo	Underwriting Acquisition And Insurance Expenses UnderwritingAcquisitionAndInsuranceExpenses	180200000	USD
CY2019	argo	Underwriting Acquisition And Insurance Expenses UnderwritingAcquisitionAndInsuranceExpenses	666000000.0	USD
CY2019Q4	us-gaap	Interest Expense InterestExpense	8400000	USD
CY2019	us-gaap	Interest Expense InterestExpense	34100000	USD
CY2019Q4	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	4500000	USD
CY2019	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	9800000	USD
CY2019Q4	us-gaap	Benefits Losses And Expenses BenefitsLossesAndExpenses	586800000	USD
CY2019	us-gaap	Benefits Losses And Expenses BenefitsLossesAndExpenses	1970000000.0	USD
CY2019Q4	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	-102200000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	0	USD
CY2019Q4	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	500000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	14100000	USD
CY2019Q4	us-gaap	Net Income Loss NetIncomeLoss	-102700000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	-14100000	USD
CY2019Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	-2.99
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	-0.41
CY2019Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	-2.99
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	-0.41
CY2019Q1	us-gaap	Deferred Income Tax Liabilities Net DeferredIncomeTaxLiabilitiesNet	0	USD
CY2019Q1	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	366100000	USD
CY2019Q1	us-gaap	Other Investments OtherInvestments	479900000	USD
CY2019Q1	us-gaap	Cash Cash	139700000	USD
CY2019Q1	us-gaap	Premiums Receivable At Carrying Value PremiumsReceivableAtCarryingValue	645200000	USD
CY2019Q1	us-gaap	Reinsurance Recoverables On Paid And Unpaid Losses ReinsuranceRecoverablesOnPaidAndUnpaidLosses	2689200000	USD
CY2019Q1	us-gaap	Income Taxes Receivable IncomeTaxesReceivable	0	USD
CY2019Q1	us-gaap	Deferred Income Tax Assets Net DeferredIncomeTaxAssetsNet	1300000	USD
CY2019Q1	argo	Accrued Underwriting Expenses And Other Liabilities AccruedUnderwritingExpensesAndOtherLiabilities	263000000.0	USD
CY2019Q1	us-gaap	Reinsurance Payable ReinsurancePayable	969200000	USD
CY2019Q1	us-gaap	Policyholder Contract Deposits PolicyholderContractDeposits	44400000	USD
CY2019Q1	us-gaap	Accrued Income Taxes AccruedIncomeTaxes	2400000	USD
CY2019Q1	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	850900000	USD
CY2018Q1	us-gaap	Other Investments OtherInvestments	544400000	USD
CY2018Q1	us-gaap	Premiums Receivable At Carrying Value PremiumsReceivableAtCarryingValue	594000000.0	USD
CY2018Q1	us-gaap	Income Taxes Receivable IncomeTaxesReceivable	200000	USD
CY2018	us-gaap	Premiums Earned Net PremiumsEarnedNet	1731500000	USD
CY2018Q1	us-gaap	Other Assets OtherAssets	309800000	USD
CY2018Q1	argo	Accrued Underwriting Expenses And Other Liabilities AccruedUnderwritingExpensesAndOtherLiabilities	146600000	USD
CY2018Q1	us-gaap	Reinsurance Payable ReinsurancePayable	734400000	USD
CY2018Q1	us-gaap	Deferred Income Tax Liabilities Net DeferredIncomeTaxLiabilitiesNet	33200000	USD
CY2018Q1	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	970200000	USD
CY2018	us-gaap	Net Investment Income NetInvestmentIncome	132300000	USD
CY2018	us-gaap	Revenues Revenues	1800800000	USD
CY2018	argo	Underwriting Acquisition And Insurance Expenses UnderwritingAcquisitionAndInsuranceExpenses	656100000	USD
CY2018	us-gaap	Interest Expense InterestExpense	31900000	USD
CY2018	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	-3900000	USD
CY2018	us-gaap	Benefits Losses And Expenses BenefitsLossesAndExpenses	1739800000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	61000000.0	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	4000000.0	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	57000000.0	USD
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.68
CY2020Q3	us-gaap	Reinsurance Payable ReinsurancePayable	1085700000	USD
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.65
CY2020Q3	us-gaap	Premiums Receivable At Carrying Value PremiumsReceivableAtCarryingValue	790200000	USD
CY2020Q3	us-gaap	Income Taxes Receivable IncomeTaxesReceivable	7500000	USD
CY2020Q3	us-gaap	Deferred Income Tax Assets Net DeferredIncomeTaxAssetsNet	14800000	USD
CY2020Q3	us-gaap	Other Assets OtherAssets	358600000	USD
CY2020Q3	us-gaap	Assets Assets	10721700000	USD
CY2020Q3	argo	Accrued Underwriting Expenses And Other Liabilities AccruedUnderwritingExpensesAndOtherLiabilities	205300000	USD
CY2020Q3	us-gaap	Liabilities Liabilities	8873000000.0	USD
CY2020Q3	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	698400000	USD
CY2020Q3	us-gaap	Stockholders Equity StockholdersEquity	1848700000	USD
CY2020Q3	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	10721700000	USD
CY2020Q3	us-gaap	Realized Investment Gains Losses RealizedInvestmentGainsLosses	-5700000	USD
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CY2020Q3	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	10500000	USD
	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	-13700000	USD
CY2020Q3	us-gaap	Gain Loss On Investments GainLossOnInvestments	-5700000	USD
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CY2020Q3	us-gaap	Revenues Revenues	483500000	USD
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CY2020Q3	argo	Underwriting Acquisition And Insurance Expenses UnderwritingAcquisitionAndInsuranceExpenses	164500000	USD
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CY2020Q3	us-gaap	Interest Expense InterestExpense	6900000	USD
	us-gaap	Interest Expense InterestExpense	21700000	USD
CY2020Q3	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	-8400000	USD
	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	-13600000	USD
CY2020Q3	us-gaap	Benefits Losses And Expenses BenefitsLossesAndExpenses	510000000.0	USD
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CY2020Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	-26500000	USD
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CY2020Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-3400000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	6900000	USD
	us-gaap	Net Income Loss NetIncomeLoss	-53200000	USD
CY2020Q3	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	-25100000	USD
CY2020Q2	us-gaap	Deferred Income Tax Assets Net DeferredIncomeTaxAssetsNet	15900000	USD
CY2020Q2	us-gaap	Other Assets OtherAssets	414500000	USD
CY2020Q3	us-gaap	Net Income Loss NetIncomeLoss	-23100000	USD
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CY2020Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	-0.72
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CY2020Q2	us-gaap	Premiums Receivable At Carrying Value PremiumsReceivableAtCarryingValue	785000000.0	USD
CY2020Q2	us-gaap	Assets Assets	10378300000	USD
CY2020Q2	argo	Accrued Underwriting Expenses And Other Liabilities AccruedUnderwritingExpensesAndOtherLiabilities	157000000.0	USD
CY2020Q2	us-gaap	Reinsurance Payable ReinsurancePayable	1038000000.0	USD
CY2020Q2	us-gaap	Accrued Income Taxes AccruedIncomeTaxes	33500000	USD
CY2020Q2	us-gaap	Liabilities Liabilities	8670600000	USD
	us-gaap	Interest Expense InterestExpense	14800000	USD
CY2020Q2	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	734400000	USD
CY2020Q2	us-gaap	Stockholders Equity StockholdersEquity	1707700000	USD
CY2020Q2	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	10378300000	USD
CY2020Q2	us-gaap	Net Investment Income NetInvestmentIncome	1400000	USD
	us-gaap	Net Investment Income NetInvestmentIncome	37000000.0	USD
CY2020Q2	us-gaap	Realized Investment Gains Losses RealizedInvestmentGainsLosses	11100000	USD
	us-gaap	Realized Investment Gains Losses RealizedInvestmentGainsLosses	38900000	USD
CY2020Q2	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	15100000	USD
	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	-24200000	USD
CY2020Q2	us-gaap	Gain Loss On Investments GainLossOnInvestments	18400000	USD
	us-gaap	Gain Loss On Investments GainLossOnInvestments	-17800000	USD
CY2020Q2	us-gaap	Revenues Revenues	455200000	USD
	us-gaap	Revenues Revenues	891700000	USD
CY2020Q2	argo	Underwriting Acquisition And Insurance Expenses UnderwritingAcquisitionAndInsuranceExpenses	161300000	USD
	argo	Underwriting Acquisition And Insurance Expenses UnderwritingAcquisitionAndInsuranceExpenses	329400000	USD
CY2020Q2	us-gaap	Interest Expense InterestExpense	7000000.0	USD
CY2020Q2	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	-4300000	USD
	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	-5200000	USD
CY2020Q2	us-gaap	Benefits Losses And Expenses BenefitsLossesAndExpenses	449300000	USD
	us-gaap	Benefits Losses And Expenses BenefitsLossesAndExpenses	911500000	USD
CY2020Q2	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	5900000	USD
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	-19800000	USD
CY2020Q2	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	11300000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	10300000	USD
CY2020Q2	us-gaap	Net Income Loss NetIncomeLoss	-5400000	USD
	us-gaap	Net Income Loss NetIncomeLoss	-30100000	USD
CY2020Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	-0.16
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CY2020Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	-0.16
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CY2020Q1	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	144500000	USD
CY2020Q1	us-gaap	Other Investments OtherInvestments	412500000	USD
CY2020Q1	argo	Underwriting Acquisition And Insurance Expenses UnderwritingAcquisitionAndInsuranceExpenses	168100000	USD
CY2020Q1	us-gaap	Investments Investments	4813100000	USD
CY2020Q1	us-gaap	Premiums Receivable At Carrying Value PremiumsReceivableAtCarryingValue	718200000	USD
CY2020Q1	us-gaap	Deferred Income Tax Assets Net DeferredIncomeTaxAssetsNet	40900000	USD
CY2020Q1	us-gaap	Other Assets OtherAssets	434800000	USD
CY2020Q1	us-gaap	Assets Assets	10177900000	USD
CY2020Q1	argo	Accrued Underwriting Expenses And Other Liabilities AccruedUnderwritingExpensesAndOtherLiabilities	187400000	USD
CY2020Q1	us-gaap	Reinsurance Payable ReinsurancePayable	1086000000.0	USD
CY2020Q1	us-gaap	Accrued Income Taxes AccruedIncomeTaxes	24300000	USD
CY2020Q1	us-gaap	Liabilities Liabilities	8564400000	USD
CY2020Q1	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	750400000	USD
CY2020Q1	us-gaap	Stockholders Equity StockholdersEquity	1613500000	USD
CY2020Q1	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	10177900000	USD
CY2020Q1	us-gaap	Net Investment Income NetInvestmentIncome	35600000	USD
CY2020Q1	us-gaap	Realized Investment Gains Losses RealizedInvestmentGainsLosses	27800000	USD
CY2020Q1	us-gaap	Gain Loss On Investments GainLossOnInvestments	-36200000	USD
CY2020Q1	us-gaap	Revenues Revenues	436500000	USD
CY2020Q1	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-1000000.0	USD
CY2020Q1	us-gaap	Interest Expense InterestExpense	7800000	USD
CY2020Q1	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	-900000	USD
CY2020Q1	us-gaap	Benefits Losses And Expenses BenefitsLossesAndExpenses	462200000	USD
CY2020Q1	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	-25700000	USD
CY2020Q1	us-gaap	Net Income Loss NetIncomeLoss	-24700000	USD
CY2020Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	-0.72
CY2020Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	-0.72
CY2019Q3	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	412200000	USD
CY2019Q3	us-gaap	Other Investments OtherInvestments	490100000	USD
CY2019Q3	us-gaap	Investments Investments	5128700000	USD
CY2019Q3	us-gaap	Premiums Receivable At Carrying Value PremiumsReceivableAtCarryingValue	727500000	USD
CY2019Q3	us-gaap	Income Taxes Receivable IncomeTaxesReceivable	0	USD
CY2019Q3	us-gaap	Other Assets OtherAssets	390500000	USD
CY2019Q3	us-gaap	Assets Assets	10434400000	USD
CY2019Q3	argo	Accrued Underwriting Expenses And Other Liabilities AccruedUnderwritingExpensesAndOtherLiabilities	285700000	USD
CY2019Q3	us-gaap	Deferred Income Tax Liabilities Net DeferredIncomeTaxLiabilitiesNet	17800000	USD
CY2019Q3	us-gaap	Liabilities Liabilities	8559000000.0	USD
CY2019Q3	us-gaap	Reinsurance Payable ReinsurancePayable	1172800000	USD
CY2019Q3	us-gaap	Accrued Income Taxes AccruedIncomeTaxes	9800000	USD
CY2019Q3	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	907000000.0	USD
CY2019Q3	us-gaap	Stockholders Equity StockholdersEquity	1875400000	USD
CY2019Q3	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	10434400000	USD
CY2019Q3	us-gaap	Premiums Earned Net PremiumsEarnedNet	451500000	USD
	us-gaap	Premiums Earned Net PremiumsEarnedNet	1303900000	USD
CY2019Q3	us-gaap	Revenues Revenues	487400000	USD
	us-gaap	Revenues Revenues	1485400000	USD
CY2019Q3	argo	Underwriting Acquisition And Insurance Expenses UnderwritingAcquisitionAndInsuranceExpenses	164000000.0	USD
	argo	Underwriting Acquisition And Insurance Expenses UnderwritingAcquisitionAndInsuranceExpenses	485800000	USD
CY2019Q3	us-gaap	Interest Expense InterestExpense	7700000	USD
	us-gaap	Interest Expense InterestExpense	25700000	USD
CY2019Q3	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	900000	USD
	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	5300000	USD
CY2019Q3	us-gaap	Benefits Losses And Expenses BenefitsLossesAndExpenses	514500000	USD
	us-gaap	Benefits Losses And Expenses BenefitsLossesAndExpenses	1383200000	USD
CY2019Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	-27100000	USD
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	102200000	USD
CY2019Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-1100000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	13600000	USD
CY2019Q3	us-gaap	Net Income Loss NetIncomeLoss	-26000000.0	USD
	us-gaap	Net Income Loss NetIncomeLoss	88600000	USD
CY2019Q3	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	-26000000.0	USD
	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	88600000	USD
CY2019Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	-0.76
	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.59
CY2019Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	-0.76
	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.55
CY2019Q2	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	432600000	USD
CY2019Q2	us-gaap	Other Investments OtherInvestments	499500000	USD
CY2019Q2	us-gaap	Investments Investments	4879300000	USD
CY2019Q2	us-gaap	Premiums Receivable At Carrying Value PremiumsReceivableAtCarryingValue	716800000	USD
CY2019Q2	us-gaap	Income Taxes Receivable IncomeTaxesReceivable	0	USD
CY2019Q2	us-gaap	Assets Assets	10153400000	USD
CY2019Q2	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	3800000	USD
CY2019Q2	argo	Accrued Underwriting Expenses And Other Liabilities AccruedUnderwritingExpensesAndOtherLiabilities	281000000.0	USD
CY2019Q2	us-gaap	Reinsurance Payable ReinsurancePayable	1050800000	USD
CY2019Q2	us-gaap	Accrued Income Taxes AccruedIncomeTaxes	6200000	USD
CY2019Q2	us-gaap	Deferred Income Tax Liabilities Net DeferredIncomeTaxLiabilitiesNet	23400000	USD
CY2019Q2	us-gaap	Liabilities Liabilities	8241500000	USD
CY2019Q2	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	942800000	USD
CY2019Q2	us-gaap	Stockholders Equity StockholdersEquity	1911900000	USD
CY2019Q2	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	10153400000	USD
CY2019Q2	us-gaap	Premiums Earned Net PremiumsEarnedNet	431700000	USD
	us-gaap	Premiums Earned Net PremiumsEarnedNet	852400000	USD
CY2019Q2	us-gaap	Revenues Revenues	488600000	USD
	us-gaap	Revenues Revenues	998000000.0	USD
CY2019Q2	argo	Underwriting Acquisition And Insurance Expenses UnderwritingAcquisitionAndInsuranceExpenses	161600000	USD
	argo	Underwriting Acquisition And Insurance Expenses UnderwritingAcquisitionAndInsuranceExpenses	321800000	USD
CY2019Q2	us-gaap	Interest Expense InterestExpense	9400000	USD
	us-gaap	Interest Expense InterestExpense	18000000.0	USD
CY2019Q1	us-gaap	Premiums Receivable At Carrying Value PremiumsReceivableAtCarryingValue	664900000	USD
	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	4400000	USD
CY2019Q2	us-gaap	Benefits Losses And Expenses BenefitsLossesAndExpenses	460800000	USD
	us-gaap	Benefits Losses And Expenses BenefitsLossesAndExpenses	868700000	USD
CY2019Q2	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	27800000	USD
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	129300000	USD
CY2019Q2	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	800000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	14700000	USD
CY2019Q2	us-gaap	Net Income Loss NetIncomeLoss	27000000.0	USD
	us-gaap	Net Income Loss NetIncomeLoss	114600000	USD
CY2019Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.79
	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.36
CY2019Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.78
	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.30
CY2019Q1	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	414800000	USD
CY2019Q1	us-gaap	Other Investments OtherInvestments	473400000	USD
CY2019Q1	us-gaap	Investments Investments	4905200000	USD
CY2019Q1	us-gaap	Income Taxes Receivable IncomeTaxesReceivable	0	USD
CY2019Q1	us-gaap	Assets Assets	9942900000	USD
CY2019Q1	argo	Accrued Underwriting Expenses And Other Liabilities AccruedUnderwritingExpensesAndOtherLiabilities	249500000	USD
CY2019Q1	us-gaap	Reinsurance Payable ReinsurancePayable	1046400000	USD
CY2019Q1	us-gaap	Accrued Income Taxes AccruedIncomeTaxes	5100000	USD
CY2019Q1	us-gaap	Deferred Income Tax Liabilities Net DeferredIncomeTaxLiabilitiesNet	18700000	USD
CY2019Q1	us-gaap	Liabilities Liabilities	8077600000	USD
CY2019Q1	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	927700000	USD
CY2019Q1	us-gaap	Stockholders Equity StockholdersEquity	1865300000	USD
CY2019Q1	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	9942900000	USD
CY2019Q1	us-gaap	Premiums Earned Net PremiumsEarnedNet	420700000	USD
CY2019Q1	us-gaap	Revenues Revenues	509400000	USD
CY2019Q1	us-gaap	Interest Expense InterestExpense	8600000	USD
CY2019Q1	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	600000	USD
CY2019Q1	us-gaap	Benefits Losses And Expenses BenefitsLossesAndExpenses	407900000	USD
CY2019Q1	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	101500000	USD
CY2019Q1	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	13900000	USD
CY2019Q1	us-gaap	Net Income Loss NetIncomeLoss	87600000	USD
CY2019Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2580000
CY2019Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2520000
CY2020Q4	argo	Fair Value Of Investments Assets Managed On Behalf Of Trade Capital Providers FairValueOfInvestmentsAssetsManagedOnBehalfOfTradeCapitalProviders	140300000	USD
CY2019Q4	argo	Fair Value Of Investments Assets Managed On Behalf Of Trade Capital Providers FairValueOfInvestmentsAssetsManagedOnBehalfOfTradeCapitalProviders	156800000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount	324900000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Fair Value HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue	329700000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount	1743600000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	1791900000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsNetCarryingAmount	607800000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	639300000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsNetCarryingAmount	82200000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue	85900000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities Without Single Maturity Date Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesWithoutSingleMaturityDateNetCarryingAmount	1222600000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities Without Single Maturity Date Fair Value HeldToMaturitySecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue	1260300000	USD
CY2020Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	3981100000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	4107100000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Number Of Positions DebtSecuritiesAvailableForSaleUnrealizedLossPositionNumberOfPositions	5301	security
CY2020Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months Number Of Positions DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsNumberOfPositions	928	property
CY2020Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer Number Of Positions DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerNumberOfPositions	149	property
CY2019Q4	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	0	USD
CY2020	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Not Previously Recorded DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded	15900000	USD
CY2020	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Securities Sold DebtSecuritiesAvailableForSaleAllowanceForCreditLossSecuritiesSold	-39300000	USD
CY2020	argo	Debt Securities Available For Sale Allowance For Credit Loss Additional Period Increase Decrease DebtSecuritiesAvailableForSaleAllowanceForCreditLossAdditionalPeriodIncreaseDecrease	23100000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	6600000	USD
CY2019	us-gaap	Other Than Temporary Impairment Loss Debt Securities Portion Recognized In Earnings OtherThanTemporaryImpairmentLossDebtSecuritiesPortionRecognizedInEarnings	20300000	USD
CY2020	us-gaap	Investment Income Interest InvestmentIncomeInterest	108600000	USD
CY2019	us-gaap	Investment Income Interest InvestmentIncomeInterest	129500000	USD
CY2018	us-gaap	Investment Income Interest InvestmentIncomeInterest	115000000.0	USD
CY2020	us-gaap	Investment Income Dividend InvestmentIncomeDividend	2800000	USD
CY2019	us-gaap	Investment Income Dividend InvestmentIncomeDividend	11100000	USD
CY2018	us-gaap	Investment Income Dividend InvestmentIncomeDividend	12500000	USD
CY2020	argo	Income On Alternative Investments IncomeOnAlternativeInvestments	10400000	USD
CY2019	argo	Income On Alternative Investments IncomeOnAlternativeInvestments	22400000	USD
CY2018	argo	Income On Alternative Investments IncomeOnAlternativeInvestments	19000000.0	USD
CY2020	argo	Income On Short Term And Other Investments IncomeOnShortTermAndOtherInvestments	3900000	USD
CY2019	argo	Income On Short Term And Other Investments IncomeOnShortTermAndOtherInvestments	8900000	USD
CY2018	argo	Income On Short Term And Other Investments IncomeOnShortTermAndOtherInvestments	9500000	USD
CY2020	us-gaap	Insurance Investment Income InsuranceInvestmentIncome	125700000	USD
CY2019	us-gaap	Insurance Investment Income InsuranceInvestmentIncome	171900000	USD
CY2018	us-gaap	Insurance Investment Income InsuranceInvestmentIncome	156000000.0	USD
CY2020	us-gaap	Investment Income Investment Expense InvestmentIncomeInvestmentExpense	13000000.0	USD
CY2019	us-gaap	Investment Income Investment Expense InvestmentIncomeInvestmentExpense	20800000	USD
CY2018	us-gaap	Investment Income Investment Expense InvestmentIncomeInvestmentExpense	23700000	USD
CY2020	us-gaap	Net Investment Income NetInvestmentIncome	112700000	USD
CY2019	us-gaap	Net Investment Income NetInvestmentIncome	151100000	USD
CY2018	us-gaap	Net Investment Income NetInvestmentIncome	132300000	USD
CY2020	argo	Gross Realized Investment On Fixed Maturities And Other Gains GrossRealizedInvestmentOnFixedMaturitiesAndOtherGains	163200000	USD
CY2019	argo	Gross Realized Investment On Fixed Maturities And Other Gains GrossRealizedInvestmentOnFixedMaturitiesAndOtherGains	55300000	USD
CY2018	argo	Gross Realized Investment On Fixed Maturities And Other Gains GrossRealizedInvestmentOnFixedMaturitiesAndOtherGains	59300000	USD
CY2020	argo	Gross Realized Investment On Fixed Maturities And Other Losses GrossRealizedInvestmentOnFixedMaturitiesAndOtherLosses	163600000	USD
CY2019	argo	Gross Realized Investment On Fixed Maturities And Other Losses GrossRealizedInvestmentOnFixedMaturitiesAndOtherLosses	63300000	USD
CY2018	argo	Gross Realized Investment On Fixed Maturities And Other Losses GrossRealizedInvestmentOnFixedMaturitiesAndOtherLosses	63600000	USD
CY2020	us-gaap	Equity Securities Fv Ni Realized Gain Loss EquitySecuritiesFvNiRealizedGainLoss	-17100000	USD
CY2019	us-gaap	Equity Securities Fv Ni Realized Gain Loss EquitySecuritiesFvNiRealizedGainLoss	128900000	USD
CY2018	us-gaap	Equity Securities Fv Ni Realized Gain Loss EquitySecuritiesFvNiRealizedGainLoss	37400000	USD
CY2020	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	10300000	USD
CY2019	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	-40800000	USD
CY2018	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	-105100000	USD
CY2020	us-gaap	Equity Securities Fv Ni Gain Loss EquitySecuritiesFvNiGainLoss	-6800000	USD
CY2019	us-gaap	Equity Securities Fv Ni Gain Loss EquitySecuritiesFvNiGainLoss	88100000	USD
CY2018	us-gaap	Equity Securities Fv Ni Gain Loss EquitySecuritiesFvNiGainLoss	-67700000	USD
CY2020	us-gaap	Gain Loss On Investments GainLossOnInvestments	-7200000	USD
CY2019	us-gaap	Gain Loss On Investments GainLossOnInvestments	80100000	USD
CY2018	us-gaap	Gain Loss On Investments GainLossOnInvestments	-72000000.0	USD
CY2020	argo	Income Tax Expense Benefit Related To Net Realized Investment And Other Gains IncomeTaxExpenseBenefitRelatedToNetRealizedInvestmentAndOtherGains	1300000	USD
CY2019	argo	Gains Losses In Investment Unrealized Appreciation Depreciation Before Tax GainsLossesInInvestmentUnrealizedAppreciationDepreciationBeforeTax	97900000	USD
CY2018	argo	Gains Losses In Investment Unrealized Appreciation Depreciation Before Tax GainsLossesInInvestmentUnrealizedAppreciationDepreciationBeforeTax	-88500000	USD
CY2019	argo	Income Tax Expense Benefit Related To Net Realized Investment And Other Gains IncomeTaxExpenseBenefitRelatedToNetRealizedInvestmentAndOtherGains	16200000	USD
CY2018	argo	Income Tax Expense Benefit Related To Net Realized Investment And Other Gains IncomeTaxExpenseBenefitRelatedToNetRealizedInvestmentAndOtherGains	11200000	USD
CY2020	argo	Net Realized Investment Gains Losses Net Of Income Taxes NetRealizedInvestmentGainsLossesNetOfIncomeTaxes	-8500000	USD
CY2019	argo	Net Realized Investment Gains Losses Net Of Income Taxes NetRealizedInvestmentGainsLossesNetOfIncomeTaxes	63900000	USD
CY2018	argo	Net Realized Investment Gains Losses Net Of Income Taxes NetRealizedInvestmentGainsLossesNetOfIncomeTaxes	-83200000	USD
CY2020	argo	Gains Losses In Investment Unrealized Appreciation Depreciation Before Tax GainsLossesInInvestmentUnrealizedAppreciationDepreciationBeforeTax	82400000	USD
CY2020	argo	Income Tax Expense Benefit Related To Unrealized Appreciation Depreciation Net Tax Effects IncomeTaxExpenseBenefitRelatedToUnrealizedAppreciationDepreciationNetTaxEffects	16500000	USD
CY2019	argo	Income Tax Expense Benefit Related To Unrealized Appreciation Depreciation Net Tax Effects IncomeTaxExpenseBenefitRelatedToUnrealizedAppreciationDepreciationNetTaxEffects	15400000	USD
CY2018	argo	Income Tax Expense Benefit Related To Unrealized Appreciation Depreciation Net Tax Effects IncomeTaxExpenseBenefitRelatedToUnrealizedAppreciationDepreciationNetTaxEffects	-13000000.0	USD
CY2020	argo	Gains Losses In Investment Unrealized Appreciation Depreciation After Tax GainsLossesInInvestmentUnrealizedAppreciationDepreciationAfterTax	65900000	USD
CY2019	argo	Gains Losses In Investment Unrealized Appreciation Depreciation After Tax GainsLossesInInvestmentUnrealizedAppreciationDepreciationAfterTax	82500000	USD
CY2018	argo	Gains Losses In Investment Unrealized Appreciation Depreciation After Tax GainsLossesInInvestmentUnrealizedAppreciationDepreciationAfterTax	-75500000	USD
CY2020Q4	us-gaap	Pledged Assets Separately Reported Securities Pledged Under Letter Of Credit Facilities At Fair Value PledgedAssetsSeparatelyReportedSecuritiesPledgedUnderLetterOfCreditFacilitiesAtFairValue	189400000	USD
CY2019Q4	us-gaap	Pledged Assets Separately Reported Securities Pledged Under Letter Of Credit Facilities At Fair Value PledgedAssetsSeparatelyReportedSecuritiesPledgedUnderLetterOfCreditFacilitiesAtFairValue	169900000	USD
CY2020Q4	argo	Securities And Letters Of Credit Pledged SecuritiesAndLettersOfCreditPledged	409200000	USD
CY2019Q4	argo	Securities And Letters Of Credit Pledged SecuritiesAndLettersOfCreditPledged	412800000	USD
CY2020Q4	us-gaap	Pledged Assets Separately Reported Securities Pledged As Collateral At Fair Value PledgedAssetsSeparatelyReportedSecuritiesPledgedAsCollateralAtFairValue	826100000	USD
CY2019Q4	us-gaap	Pledged Assets Separately Reported Securities Pledged As Collateral At Fair Value PledgedAssetsSeparatelyReportedSecuritiesPledgedAsCollateralAtFairValue	775200000	USD
CY2019Q4	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Value FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue	25600000	USD
CY2020	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Transfers Into Level3 FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3	0	USD
CY2020	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Transfers Out Of Level3 FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3	0	USD
CY2020	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Gain Loss Included In Earnings1 FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1	-5900000	USD
CY2020	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Gain Loss Included In Other Comprehensive Income Loss FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss	-500000	USD
CY2020	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Purchases FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases	5300000	USD
CY2020	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Issues FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetIssues	0	USD
CY2020	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Sales FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales	0	USD
CY2020	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Settlements FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements	0	USD
CY2020Q4	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Value FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue	24500000	USD
CY2020	argo	Amount Of Gains Or Losses For Period Included In Net Income Attributable To Change In Unrealized Gains Or Losses Relating To Assets Held At End Of Period AmountOfGainsOrLossesForPeriodIncludedInNetIncomeAttributableToChangeInUnrealizedGainsOrLossesRelatingToAssetsHeldAtEndOfPeriod	0	USD
CY2018Q4	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Value FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue	22000000.0	USD
CY2019	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Transfers Into Level3 FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3	3500000	USD
CY2019	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Transfers Out Of Level3 FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3	0	USD
CY2019	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Gain Loss Included In Earnings1 FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1	-2000000.0	USD
CY2019	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Gain Loss Included In Other Comprehensive Income Loss FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss	600000	USD
CY2019	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Purchases FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases	1900000	USD
CY2019	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Issues FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetIssues	0	USD
CY2019	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Sales FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales	400000	USD
CY2019	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Settlements FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements	0	USD
CY2019Q4	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Value FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue	25600000	USD
CY2019	argo	Amount Of Gains Or Losses For Period Included In Net Income Attributable To Change In Unrealized Gains Or Losses Relating To Assets Held At End Of Period AmountOfGainsOrLossesForPeriodIncludedInNetIncomeAttributableToChangeInUnrealizedGainsOrLossesRelatingToAssetsHeldAtEndOfPeriod	0	USD
CY2019Q4	us-gaap	Premiums Receivable At Carrying Value PremiumsReceivableAtCarryingValue	676500000	USD
CY2019Q4	us-gaap	Premiums Receivable Allowance For Doubtful Accounts PremiumsReceivableAllowanceForDoubtfulAccounts	7900000	USD
CY2020	us-gaap	Premium Receivable Credit Loss Expense Reversal PremiumReceivableCreditLossExpenseReversal	3600000	USD
CY2020	us-gaap	Premiums Receivable Allowance For Doubtful Accounts Write Offs Against Allowance PremiumsReceivableAllowanceForDoubtfulAccountsWriteOffsAgainstAllowance	2400000	USD
CY2020	argo	Premium Receivable Allowance For Credit Loss Foreign Exchange Adjustments PremiumReceivableAllowanceForCreditLossForeignExchangeAdjustments	300000	USD
CY2020Q4	us-gaap	Premiums Receivable At Carrying Value PremiumsReceivableAtCarryingValue	679800000	USD
CY2020Q4	us-gaap	Premiums Receivable Allowance For Doubtful Accounts PremiumsReceivableAllowanceForDoubtfulAccounts	9400000	USD
CY2019Q4	us-gaap	Reinsurance Recoverables ReinsuranceRecoverables	3107200000	USD
CY2019Q4	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	1100000	USD
CY2020	us-gaap	Reinsurance Recoverable Credit Loss Expense Reversal ReinsuranceRecoverableCreditLossExpenseReversal	900000	USD
CY2020	us-gaap	Reinsurance Loss On Uncollectible Accounts In Period Amount ReinsuranceLossOnUncollectibleAccountsInPeriodAmount	400000	USD
CY2020Q4	us-gaap	Reinsurance Recoverables ReinsuranceRecoverables	3009000000.0	USD
CY2020Q4	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	4100000	USD
CY2020Q4	argo	Credit Risk Rating Percent Rated A Or Better CreditRiskRatingPercentRatedAOrBetter	0.903
CY2020	us-gaap	Lease Cost LeaseCost	20300000	USD
CY2019	us-gaap	Lease Cost LeaseCost	23400000	USD
CY2020Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	82000000.0	USD
CY2019Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	91800000	USD
CY2020Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	95800000	USD
CY2019Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	105700000	USD
CY2019	us-gaap	Operating Lease Payments OperatingLeasePayments	17500000	USD
CY2020Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P10Y6M
CY2019Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P9Y10M28D
CY2020Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.0377
CY2019	us-gaap	Variable Lease Cost VariableLeaseCost	4500000	USD
CY2020	us-gaap	Sublease Income SubleaseIncome	400000	USD
CY2019Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.0386
CY2020	us-gaap	Operating Lease Cost OperatingLeaseCost	15300000	USD
CY2019	us-gaap	Operating Lease Cost OperatingLeaseCost	19300000	USD
CY2020	us-gaap	Variable Lease Cost VariableLeaseCost	5400000	USD
CY2019	us-gaap	Sublease Income SubleaseIncome	400000	USD
CY2020	us-gaap	Lease Cost LeaseCost	20300000	USD
CY2019	us-gaap	Lease Cost LeaseCost	23400000	USD
CY2020	us-gaap	Operating Lease Payments OperatingLeasePayments	15700000	USD
CY2020	argo	Operating Lease Payments Liability Reduction OperatingLeasePaymentsLiabilityReduction	12800000	USD
CY2019	argo	Operating Lease Payments Liability Reduction OperatingLeasePaymentsLiabilityReduction	18300000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Next Twelve Months LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths	14700000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Two LesseeOperatingLeaseLiabilityPaymentsDueYearTwo	13200000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Three LesseeOperatingLeaseLiabilityPaymentsDueYearThree	11100000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Four LesseeOperatingLeaseLiabilityPaymentsDueYearFour	9800000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Five LesseeOperatingLeaseLiabilityPaymentsDueYearFive	9600000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due After Year Five LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive	58400000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	116800000	USD
CY2020Q4	argo	Lessee Operating Lease Lease Notyet Commenced Liability LesseeOperatingLeaseLeaseNotyetCommencedLiability	0	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	21000000.0	USD
CY2020Q4	argo	Collateral Under Reinsurance Agreements CollateralUnderReinsuranceAgreements	1131400000	USD
CY2019Q4	argo	Collateral Under Reinsurance Agreements CollateralUnderReinsuranceAgreements	1184700000	USD
CY2020Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	95800000	USD
CY2020	argo	Numberof Leased Properties Shortterm NumberofLeasedPropertiesShortterm	1	property
CY2020	argo	Numberof Leased Properties Shortterm NumberofLeasedPropertiesShortterm	1	property
CY2020	us-gaap	Operating Lease Lease Income OperatingLeaseLeaseIncome	2600000	USD
CY2019	us-gaap	Operating Lease Lease Income OperatingLeaseLeaseIncome	2800000	USD
CY2020Q4	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	4100000	USD
CY2019Q4	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	1100000	USD
CY2020Q4	argo	Collateral Under Reinsurance Agreements CollateralUnderReinsuranceAgreements	1131400000	USD
CY2019Q4	argo	Collateral Under Reinsurance Agreements CollateralUnderReinsuranceAgreements	1184700000	USD
CY2020Q4	us-gaap	Reinsurance Recoverables On Paid Losses ReinsuranceRecoverablesOnPaidLosses	509100000	USD
CY2020Q4	us-gaap	Reinsurance Recoverables On Paid Losses ReinsuranceRecoverablesOnPaidLosses	509100000	USD
CY2019Q4	us-gaap	Reinsurance Recoverables On Paid Losses ReinsuranceRecoverablesOnPaidLosses	672300000	USD
CY2019Q4	us-gaap	Reinsurance Recoverables On Paid Losses ReinsuranceRecoverablesOnPaidLosses	672300000	USD
CY2020	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Incurred Claims1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaims1	1208800000	USD
CY2019	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Incurred Claims1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaims1	1220700000	USD
CY2020	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Incurred Claims1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaims1	1208800000	USD
CY2019	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Incurred Claims1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaims1	1220700000	USD
CY2018	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Incurred Claims1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaims1	1040800000	USD
CY2018	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Incurred Claims1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaims1	1040800000	USD
CY2020	us-gaap	Reinsurance Effect On Claims And Benefits Incurred Amount Ceded ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountCeded	941300000	USD
CY2020	us-gaap	Reinsurance Effect On Claims And Benefits Incurred Amount Ceded ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountCeded	941300000	USD
CY2019	us-gaap	Reinsurance Effect On Claims And Benefits Incurred Amount Ceded ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountCeded	1031100000	USD
CY2019	us-gaap	Reinsurance Effect On Claims And Benefits Incurred Amount Ceded ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountCeded	1031100000	USD
CY2018	us-gaap	Reinsurance Effect On Claims And Benefits Incurred Amount Ceded ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountCeded	888900000	USD
CY2018	us-gaap	Reinsurance Effect On Claims And Benefits Incurred Amount Ceded ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountCeded	888900000	USD
CY2020	us-gaap	Direct Premiums Written DirectPremiumsWritten	2676100000	USD
CY2019	us-gaap	Direct Premiums Written DirectPremiumsWritten	2510400000	USD
CY2018	us-gaap	Direct Premiums Written DirectPremiumsWritten	2292900000	USD
CY2020	us-gaap	Assumed Premiums Written AssumedPremiumsWritten	557200000	USD
CY2020	us-gaap	Ceded Premiums Written CededPremiumsWritten	1423200000	USD
CY2019	us-gaap	Ceded Premiums Written CededPremiumsWritten	1375500000	USD
CY2018	us-gaap	Ceded Premiums Written CededPremiumsWritten	1189000000.0	USD
CY2019	us-gaap	Assumed Premiums Written AssumedPremiumsWritten	619700000	USD
CY2018	us-gaap	Assumed Premiums Written AssumedPremiumsWritten	661400000	USD
CY2020	us-gaap	Premiums Written Net PremiumsWrittenNet	1810100000	USD
CY2019	us-gaap	Premiums Written Net PremiumsWrittenNet	1754600000	USD
CY2018	us-gaap	Premiums Written Net PremiumsWrittenNet	1765300000	USD
CY2020	us-gaap	Direct Premiums Earned DirectPremiumsEarned	2660600000	USD
CY2019	us-gaap	Direct Premiums Earned DirectPremiumsEarned	2412400000	USD
CY2018	us-gaap	Direct Premiums Earned DirectPremiumsEarned	2201000000.0	USD
CY2020	us-gaap	Ceded Premiums Earned CededPremiumsEarned	1388600000	USD
CY2019	us-gaap	Ceded Premiums Earned CededPremiumsEarned	1286700000	USD
CY2018	us-gaap	Ceded Premiums Earned CededPremiumsEarned	1137200000	USD
CY2020	us-gaap	Assumed Premiums Earned AssumedPremiumsEarned	508500000	USD
CY2019	us-gaap	Assumed Premiums Earned AssumedPremiumsEarned	604000000.0	USD
CY2018	us-gaap	Assumed Premiums Earned AssumedPremiumsEarned	667700000	USD
CY2020	us-gaap	Premiums Earned Net PremiumsEarnedNet	1780500000	USD
CY2019	us-gaap	Premiums Earned Net PremiumsEarnedNet	1729700000	USD
CY2018	us-gaap	Premiums Earned Net PremiumsEarnedNet	1731500000	USD
CY2020	us-gaap	Premiums Percentage Assumed To Net PremiumsPercentageAssumedToNet	0.286
CY2019	us-gaap	Premiums Percentage Assumed To Net PremiumsPercentageAssumedToNet	0.349
CY2018	us-gaap	Premiums Percentage Assumed To Net PremiumsPercentageAssumedToNet	0.386
CY2020	us-gaap	Schedule Of Liability For Unpaid Claims And Claims Adjustment Expense ScheduleOfLiabilityForUnpaidClaimsAndClaimsAdjustmentExpense	<div style="margin-top:6pt;text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">The following table provides a reconciliation of reserves for losses and loss adjustment expenses (“LAE”):</span></div><div style="margin-bottom:6pt;text-align:justify"><table style="border-collapse:collapse;display:inline-table;vertical-align:top;width:100.000%"><tr><td style="width:1.0%"/><td style="width:61.261%"/><td style="width:0.1%"/><td style="width:1.0%"/><td style="width:10.983%"/><td style="width:0.1%"/><td style="width:0.1%"/><td style="width:0.494%"/><td style="width:0.1%"/><td style="width:1.0%"/><td style="width:10.983%"/><td style="width:0.1%"/><td style="width:0.1%"/><td style="width:0.494%"/><td style="width:0.1%"/><td style="width:1.0%"/><td style="width:10.985%"/><td style="width:0.1%"/></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%"> </span></td><td colspan="15" style="padding:2px 1pt;text-align:center;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">For the Years Ended December 31,</span></td></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">(in millions)</span></td><td colspan="3" style="border-top:1pt solid #000000;padding:2px 1pt;text-align:center;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">2020</span></td><td colspan="3" style="border-top:1pt solid #000000;padding:0 1pt"/><td colspan="3" style="border-top:1pt solid #000000;padding:2px 1pt;text-align:center;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">2019</span></td><td colspan="3" style="border-top:1pt solid #000000;padding:0 1pt"/><td colspan="3" style="border-top:1pt solid #000000;padding:2px 1pt;text-align:center;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">2018</span></td></tr><tr><td colspan="3" style="background-color:#cceeff;padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Net reserves beginning of the year</span></td><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">$</span></td><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">2,722.7 </span></td><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">$</span></td><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">2,562.9 </span></td><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">$</span></td><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">2,488.0 </span></td><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="background-color:#ffffff;padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Net AIL reserves acquired</span></td><td colspan="2" style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">27.9 </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#ffffff;padding:0 1pt"/><td colspan="2" style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">— </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#ffffff;padding:0 1pt"/><td colspan="2" style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">— </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="background-color:#cceeff;padding:2px 1pt;text-align:left;vertical-align:bottom"><div style="margin-top:12pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">Net ArgoGlobal Assicurazioni reserves acquired</span></div></td><td colspan="2" style="background-color:#cceeff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">— </span></td><td style="background-color:#cceeff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td colspan="2" style="background-color:#cceeff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">— </span></td><td style="background-color:#cceeff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td colspan="2" style="background-color:#cceeff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">43.4 </span></td><td style="background-color:#cceeff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="background-color:#ffffff;padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Add:</span></td><td colspan="3" style="background-color:#ffffff;padding:0 1pt"/><td colspan="3" style="background-color:#ffffff;padding:0 1pt"/><td colspan="3" style="background-color:#ffffff;padding:0 1pt"/><td colspan="3" style="background-color:#ffffff;padding:0 1pt"/><td colspan="3" style="background-color:#ffffff;padding:0 1pt"/></tr><tr><td colspan="3" style="background-color:#cceeff;padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Losses and LAE incurred during current calendar year, net of reinsurance:</span></td><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/></tr><tr><td colspan="3" style="background-color:#ffffff;padding:2px 1pt 2px 12.25pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Current accident year</span></td><td colspan="2" style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">1,201.1 </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#ffffff;padding:0 1pt"/><td colspan="2" style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">1,082.6 </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#ffffff;padding:0 1pt"/><td colspan="2" style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">1,058.8 </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="background-color:#cceeff;padding:2px 1pt 2px 12.25pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Prior accident years</span></td><td colspan="2" style="background-color:#cceeff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">7.7 </span></td><td style="background-color:#cceeff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td colspan="2" style="background-color:#cceeff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">138.1 </span></td><td style="background-color:#cceeff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td colspan="2" style="background-color:#cceeff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">(18.0)</span></td><td style="background-color:#cceeff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="background-color:#ffffff;padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Losses and LAE incurred during calendar year, net of reinsurance</span></td><td colspan="2" style="background-color:#ffffff;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">1,208.8 </span></td><td style="background-color:#ffffff;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#ffffff;padding:0 1pt"/><td colspan="2" style="background-color:#ffffff;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">1,220.7 </span></td><td style="background-color:#ffffff;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#ffffff;padding:0 1pt"/><td colspan="2" style="background-color:#ffffff;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">1,040.8 </span></td><td style="background-color:#ffffff;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="background-color:#cceeff;padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Deduct:</span></td><td colspan="3" style="background-color:#cceeff;border-top:1pt solid #000000;padding:0 1pt"/><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td colspan="3" style="background-color:#cceeff;border-top:1pt solid #000000;padding:0 1pt"/><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td colspan="3" style="background-color:#cceeff;border-top:1pt solid #000000;padding:0 1pt"/></tr><tr><td colspan="3" style="background-color:#ffffff;padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Losses and LAE payments made during current calendar year, net of reinsurance:</span></td><td colspan="3" style="background-color:#ffffff;padding:0 1pt"/><td colspan="3" style="background-color:#ffffff;padding:0 1pt"/><td colspan="3" style="background-color:#ffffff;padding:0 1pt"/><td colspan="3" style="background-color:#ffffff;padding:0 1pt"/><td colspan="3" style="background-color:#ffffff;padding:0 1pt"/></tr><tr><td colspan="3" style="background-color:#cceeff;padding:2px 1pt 2px 12.25pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Current accident year</span></td><td colspan="2" style="background-color:#cceeff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">253.4 </span></td><td style="background-color:#cceeff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td colspan="2" style="background-color:#cceeff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">224.3 </span></td><td style="background-color:#cceeff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td colspan="2" style="background-color:#cceeff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">273.3 </span></td><td style="background-color:#cceeff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="background-color:#ffffff;padding:2px 1pt 2px 12.25pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Prior accident years</span></td><td colspan="2" style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">866.4 </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#ffffff;padding:0 1pt"/><td colspan="2" style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">806.0 </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#ffffff;padding:0 1pt"/><td colspan="2" style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">665.6 </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="background-color:#cceeff;padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Losses and LAE payments made during current calendar year, net of reinsurance:</span></td><td colspan="2" style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">1,119.8 </span></td><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td colspan="2" style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">1,030.3 </span></td><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td colspan="2" style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">938.9 </span></td><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="background-color:#ffffff;padding:2px 1pt;text-align:left;vertical-align:bottom"><div><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Change in participation interest </span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:6.5pt;font-weight:400;line-height:100%;position:relative;top:-3.5pt;vertical-align:baseline">(1)</span></div></td><td colspan="2" style="background-color:#ffffff;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">32.8 </span></td><td style="background-color:#ffffff;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#ffffff;padding:0 1pt"/><td colspan="2" style="background-color:#ffffff;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">(14.4)</span></td><td style="background-color:#ffffff;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#ffffff;padding:0 1pt"/><td colspan="2" style="background-color:#ffffff;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">(25.5)</span></td><td style="background-color:#ffffff;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="background-color:#cceeff;padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Foreign exchange adjustments</span></td><td colspan="2" style="background-color:#cceeff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">33.7 </span></td><td style="background-color:#cceeff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td colspan="2" style="background-color:#cceeff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">(16.2)</span></td><td style="background-color:#cceeff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td colspan="2" style="background-color:#cceeff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">(44.9)</span></td><td style="background-color:#cceeff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="background-color:#ffffff;padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Net reserves - end of year</span></td><td colspan="2" style="background-color:#ffffff;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">2,906.1 </span></td><td style="background-color:#ffffff;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#ffffff;padding:0 1pt"/><td colspan="2" style="background-color:#ffffff;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">2,722.7 </span></td><td style="background-color:#ffffff;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#ffffff;padding:0 1pt"/><td colspan="2" style="background-color:#ffffff;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">2,562.9 </span></td><td style="background-color:#ffffff;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="background-color:#cceeff;padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Add:</span></td><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/></tr><tr><td colspan="3" style="background-color:#ffffff;padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Reinsurance recoverables on unpaid losses and LAE, end of year</span></td><td colspan="2" style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">2,499.9 </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#ffffff;padding:0 1pt"/><td colspan="2" style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">2,434.9 </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#ffffff;padding:0 1pt"/><td colspan="2" style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">2,091.7 </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="background-color:#cceeff;padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Gross reserves - end of year</span></td><td style="background-color:#cceeff;border-bottom:3pt double #000000;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">$</span></td><td style="background-color:#cceeff;border-bottom:3pt double #000000;border-top:1pt solid #000000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">5,406.0 </span></td><td style="background-color:#cceeff;border-bottom:3pt double #000000;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td style="background-color:#cceeff;border-bottom:3pt double #000000;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">$</span></td><td style="background-color:#cceeff;border-bottom:3pt double #000000;border-top:1pt solid #000000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">5,157.6 </span></td><td style="background-color:#cceeff;border-bottom:3pt double #000000;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td style="background-color:#cceeff;border-bottom:3pt double #000000;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">$</span></td><td style="background-color:#cceeff;border-bottom:3pt double #000000;border-top:1pt solid #000000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">4,654.6 </span></td><td style="background-color:#cceeff;border-bottom:3pt double #000000;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr></table></div><div style="margin-top:3pt;padding-left:9pt;text-align:justify;text-indent:-9pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:6.5pt;font-weight:400;line-height:120%;position:relative;top:-3.5pt;vertical-align:baseline">(1) </span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:120%">Amount represents (decrease) increase in reserves due to change in our Syndicate 1200 and Syndicate 1910 participation.</span></div>
CY2019Q4	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Net LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	2722700000	USD
CY2018Q4	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Net LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	2562900000	USD
CY2017Q4	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Net LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	2488000000.0	USD
CY2020	argo	Liability For Unpaid Claims And Claims Adjustment Expense Acquired From Acquisition LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseAcquiredFromAcquisition	27900000	USD
CY2019	argo	Liability For Unpaid Claims And Claims Adjustment Expense Acquired From Acquisition LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseAcquiredFromAcquisition	0	USD
CY2018	argo	Liability For Unpaid Claims And Claims Adjustment Expense Acquired From Acquisition LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseAcquiredFromAcquisition	0	USD
CY2020	argo	Liability For Unpaid Claims And Claims Adjustment Expense Net Reserves Acquired LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNetReservesAcquired	0	USD
CY2019	argo	Liability For Unpaid Claims And Claims Adjustment Expense Net Reserves Acquired LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNetReservesAcquired	0	USD
CY2018	argo	Liability For Unpaid Claims And Claims Adjustment Expense Net Reserves Acquired LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNetReservesAcquired	43400000	USD
CY2020	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Current Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersCurrentYearClaimsAndClaimsAdjustmentExpense	1201100000	USD
CY2019	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Current Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersCurrentYearClaimsAndClaimsAdjustmentExpense	1082600000	USD
CY2018	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Current Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersCurrentYearClaimsAndClaimsAdjustmentExpense	1058800000	USD
CY2020	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Prior Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense	7700000	USD
CY2019	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Prior Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense	138100000	USD
CY2018	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Prior Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense	-18000000.0	USD
CY2020	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Incurred Claims1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaims1	1208800000	USD
CY2019	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Incurred Claims1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaims1	1220700000	USD
CY2018	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Incurred Claims1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaims1	1040800000	USD
CY2020	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Current Year1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidCurrentYear1	253400000	USD
CY2019	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Current Year1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidCurrentYear1	224300000	USD
CY2018	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Current Year1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidCurrentYear1	273300000	USD
CY2020	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Prior Years1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidPriorYears1	866400000	USD
CY2019	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Prior Years1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidPriorYears1	806000000.0	USD
CY2018	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Prior Years1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidPriorYears1	665600000	USD
CY2020	us-gaap	Payments For Losses And Loss Adjustment Expense PaymentsForLossesAndLossAdjustmentExpense	1119800000	USD
CY2019	us-gaap	Payments For Losses And Loss Adjustment Expense PaymentsForLossesAndLossAdjustmentExpense	1030300000	USD
CY2018	us-gaap	Payments For Losses And Loss Adjustment Expense PaymentsForLossesAndLossAdjustmentExpense	938900000	USD
CY2020	argo	Liability For Unpaid Claims And Claims Adjustment Expense Change In Participation Interest LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseChangeInParticipationInterest	32800000	USD
CY2019	argo	Liability For Unpaid Claims And Claims Adjustment Expense Change In Participation Interest LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseChangeInParticipationInterest	-14400000	USD
CY2018	argo	Liability For Unpaid Claims And Claims Adjustment Expense Change In Participation Interest LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseChangeInParticipationInterest	-25500000	USD
CY2020	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Foreign Currency Translation Gain Loss LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseForeignCurrencyTranslationGainLoss	-33700000	USD
CY2019	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Foreign Currency Translation Gain Loss LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseForeignCurrencyTranslationGainLoss	16200000	USD
CY2018	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Foreign Currency Translation Gain Loss LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseForeignCurrencyTranslationGainLoss	44900000	USD
CY2020Q4	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Net LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	2906100000	USD
CY2019Q4	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Net LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	2722700000	USD
CY2018Q4	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Net LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	2562900000	USD
CY2020Q4	us-gaap	Reinsurance Receivables Incurred But Not Reported Claims ReinsuranceReceivablesIncurredButNotReportedClaims	2499900000	USD
CY2019Q4	us-gaap	Reinsurance Receivables Incurred But Not Reported Claims ReinsuranceReceivablesIncurredButNotReportedClaims	2434900000	USD
CY2018Q4	us-gaap	Reinsurance Receivables Incurred But Not Reported Claims ReinsuranceReceivablesIncurredButNotReportedClaims	2091700000	USD
CY2020Q4	us-gaap	Liability For Claims And Claims Adjustment Expense LiabilityForClaimsAndClaimsAdjustmentExpense	5406000000.0	USD
CY2019Q4	us-gaap	Liability For Claims And Claims Adjustment Expense LiabilityForClaimsAndClaimsAdjustmentExpense	5157600000	USD
CY2018Q4	us-gaap	Liability For Claims And Claims Adjustment Expense LiabilityForClaimsAndClaimsAdjustmentExpense	4654600000	USD
CY2020	argo	Loss Adjustment Expenses Related To Pandemic LossAdjustmentExpensesRelatedToPandemic	73200000	USD
CY2020	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Prior Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense	7700000	USD
CY2019	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Prior Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense	138100000	USD
CY2018	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Prior Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense	-18000000.0	USD
CY2020	us-gaap	Number Of Reportable Segments NumberOfReportableSegments	2	segment
CY2020Q4	us-gaap	Shortduration Insurance Contracts Liability For Unpaid Claims And Allocated Claim Adjustment Expense Net ShortdurationInsuranceContractsLiabilityForUnpaidClaimsAndAllocatedClaimAdjustmentExpenseNet	2856300000	USD
CY2020Q4	us-gaap	Reinsurance Recoverable For Unpaid Claims And Claims Adjustments ReinsuranceRecoverableForUnpaidClaimsAndClaimsAdjustments	2499900000	USD
CY2020Q4	us-gaap	Shortduration Insurance Contracts Liability For Unpaid Claims And Claims Adjustment Expense Accumulated Unallocated Claim Adjustment Expense ShortdurationInsuranceContractsLiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseAccumulatedUnallocatedClaimAdjustmentExpense	67600000	USD
CY2020Q4	us-gaap	Shortduration Insurance Contracts Discounted Liabilities Aggregate Discount ShortdurationInsuranceContractsDiscountedLiabilitiesAggregateDiscount	17800000	USD
CY2020Q4	us-gaap	Liability For Claims And Claims Adjustment Expense LiabilityForClaimsAndClaimsAdjustmentExpense	5406000000.0	USD
CY2020	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	2	segment
CY2020Q4	us-gaap	Short Duration Contracts Discounted Liabilities Amount ShortDurationContractsDiscountedLiabilitiesAmount	278800000	USD
CY2019Q4	us-gaap	Short Duration Contracts Discounted Liabilities Amount ShortDurationContractsDiscountedLiabilitiesAmount	302000000.0	USD
CY2018Q4	us-gaap	Short Duration Contracts Discounted Liabilities Amount ShortDurationContractsDiscountedLiabilitiesAmount	303900000	USD
CY2020Q4	us-gaap	Shortduration Insurance Contracts Discounted Liabilities Aggregate Discount ShortdurationInsuranceContractsDiscountedLiabilitiesAggregateDiscount	17800000	USD
CY2019Q4	us-gaap	Shortduration Insurance Contracts Discounted Liabilities Aggregate Discount ShortdurationInsuranceContractsDiscountedLiabilitiesAggregateDiscount	17900000	USD
CY2018Q4	us-gaap	Shortduration Insurance Contracts Discounted Liabilities Aggregate Discount ShortdurationInsuranceContractsDiscountedLiabilitiesAggregateDiscount	16900000	USD
CY2020	us-gaap	Shortduration Insurance Contracts Discounted Liabilities Interest Accretion ShortdurationInsuranceContractsDiscountedLiabilitiesInterestAccretion	1900000	USD
CY2019	us-gaap	Shortduration Insurance Contracts Discounted Liabilities Interest Accretion ShortdurationInsuranceContractsDiscountedLiabilitiesInterestAccretion	1500000	USD
CY2018	us-gaap	Shortduration Insurance Contracts Discounted Liabilities Interest Accretion ShortdurationInsuranceContractsDiscountedLiabilitiesInterestAccretion	3400000	USD
CY2020Q4	us-gaap	Liability For Asbestos And Environmental Claims Gross LiabilityForAsbestosAndEnvironmentalClaimsGross	59300000	USD
CY2019Q4	us-gaap	Liability For Asbestos And Environmental Claims Gross LiabilityForAsbestosAndEnvironmentalClaimsGross	52600000	USD
CY2020Q4	argo	Gross Reserve For Discontinuation Of Certain Lines Of Business GrossReserveForDiscontinuationOfCertainLinesOfBusiness	236500000	USD
CY2019Q4	argo	Gross Reserve For Discontinuation Of Certain Lines Of Business GrossReserveForDiscontinuationOfCertainLinesOfBusiness	253500000	USD
CY2020	argo	Asbestos And Environmental Underwriting Losses AsbestosAndEnvironmentalUnderwritingLosses	17400000	USD
CY2019	argo	Asbestos And Environmental Underwriting Losses AsbestosAndEnvironmentalUnderwritingLosses	8300000	USD
CY2018	argo	Asbestos And Environmental Underwriting Losses AsbestosAndEnvironmentalUnderwritingLosses	8000000.0	USD
CY2020	argo	Discontinued Operation Underwriting Losses Gains DiscontinuedOperationUnderwritingLossesGains	-16100000	USD
CY2019	argo	Discontinued Operation Underwriting Losses Gains DiscontinuedOperationUnderwritingLossesGains	-14200000	USD
CY2018	argo	Discontinued Operation Underwriting Losses Gains DiscontinuedOperationUnderwritingLossesGains	-15900000	USD
CY2020Q4	us-gaap	Other Long Term Debt OtherLongTermDebt	60700000	USD
CY2019Q4	us-gaap	Other Long Term Debt OtherLongTermDebt	181300000	USD
CY2020	us-gaap	Debt Instrument Redemption Price Percentage DebtInstrumentRedemptionPricePercentage	1
CY2020Q4	us-gaap	Long Term Notes Payable LongTermNotesPayable	60700000	USD
CY2019Q4	us-gaap	Long Term Notes Payable LongTermNotesPayable	56300000	USD
CY2020Q4	us-gaap	Liability Reporting Currency Denominated Value LiabilityReportingCurrencyDenominatedValue	44200000	USD
CY2019Q4	us-gaap	Liability Reporting Currency Denominated Value LiabilityReportingCurrencyDenominatedValue	39800000	USD
CY2020Q3	argo	Depositary Shares Shares Issued DepositarySharesSharesIssued	6000000	shares
CY2020Q3	argo	Depositary Share Liquidation Preference Per Share DepositaryShareLiquidationPreferencePerShare	25
CY2020	argo	Depositary Shares Dividends Per Share Declared DepositarySharesDividendsPerShareDeclared	0.768056
CY2020Q4	us-gaap	Preferred Stock Shares Authorized PreferredStockSharesAuthorized	30000000	shares
CY2020Q4	us-gaap	Preferred Stock Par Or Stated Value Per Share PreferredStockParOrStatedValuePerShare	1.00
CY2020Q4	us-gaap	Preferred Stock Shares Outstanding PreferredStockSharesOutstanding	6000	shares
CY2020Q4	us-gaap	Preferred Stock Shares Issued PreferredStockSharesIssued	6000	shares
CY2019Q4	us-gaap	Preferred Stock Shares Issued PreferredStockSharesIssued	0	shares
CY2019Q4	us-gaap	Preferred Stock Shares Outstanding PreferredStockSharesOutstanding	0	shares
CY2020Q3	argo	Proceeds From Sale Of Depositary Shares ProceedsFromSaleOfDepositaryShares	144000000	USD
CY2020Q3	us-gaap	Extinguishment Of Debt Amount ExtinguishmentOfDebtAmount	125000000	USD
CY2020Q3	argo	Preferred Stock Per Depositary Share Amounts Of Preferred Dividends PreferredStockPerDepositaryShareAmountsOfPreferredDividends	1.75
CY2020Q3	argo	Depositary Share Liquidation Preference Per Share DepositaryShareLiquidationPreferencePerShare	25
CY2020Q3	argo	Depositary Share Liquidation Preference Per Share DepositaryShareLiquidationPreferencePerShare	25
CY2020	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.24
CY2020	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	43000000.0	USD
CY2019	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.24
CY2019	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	43100000	USD
CY2018	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.08
CY2018	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	37500000	USD
CY2019	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	0	shares
CY2020	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	0	shares
CY2019	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	72200000	USD
CY2019	us-gaap	Reclassification From Aoci Current Period Net Of Tax Attributable To Parent ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent	-8700000	USD
CY2019	argo	Other Comprehensive Income Loss Netof Tax Including Cumulative Effectof Adoption OtherComprehensiveIncomeLossNetofTaxIncludingCumulativeEffectofAdoption	80900000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	62900000	USD
CY2020	us-gaap	Reclassification From Aoci Current Period Net Of Tax Attributable To Parent ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent	12800000	USD
CY2020	argo	Other Comprehensive Income Loss Netof Tax Including Cumulative Effectof Adoption OtherComprehensiveIncomeLossNetofTaxIncludingCumulativeEffectofAdoption	50100000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	-54100000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	-14100000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	57000000.0	USD
CY2020	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	4600000	USD
CY2019	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	0	USD
CY2018	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	0	USD
CY2020	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	-58700000	USD
CY2019	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	-14100000	USD
CY2018	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	57000000.0	USD
CY2020	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	34614813	shares
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	34205954	shares
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	33922009	shares
CY2020	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	0	shares
CY2019	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	0	shares
CY2018	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	756772	shares
CY2020	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	34614813	shares
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	34205954	shares
CY2018	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	34678781	shares
CY2020	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	-1.70
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	-0.41
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.68
CY2020	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	-1.70
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	-0.41
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.65
CY2019Q4	us-gaap	Treasury Stock Shares TreasuryStockShares	11315889	shares
CY2020Q4	us-gaap	Treasury Stock Shares TreasuryStockShares	11315889	shares
CY2018Q4	us-gaap	Treasury Stock Shares TreasuryStockShares	11315889	shares
CY2020	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	197035	shares
CY2019	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	587462	shares
CY2018	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	0	shares
CY2020	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	8700000	USD
CY2020	us-gaap	Allocated Share Based Compensation Expense Net Of Tax AllocatedShareBasedCompensationExpenseNetOfTax	7800000	USD
CY2019	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	16900000	USD
CY2019	us-gaap	Allocated Share Based Compensation Expense Net Of Tax AllocatedShareBasedCompensationExpenseNetOfTax	15500000	USD
CY2018	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	18300000	USD
CY2018	us-gaap	Allocated Share Based Compensation Expense Net Of Tax AllocatedShareBasedCompensationExpenseNetOfTax	16500000	USD
CY2020	us-gaap	Noninterest Expense Commission Expense NoninterestExpenseCommissionExpense	268000000.0	USD
CY2019	us-gaap	Noninterest Expense Commission Expense NoninterestExpenseCommissionExpense	241300000	USD
CY2018	us-gaap	Noninterest Expense Commission Expense NoninterestExpenseCommissionExpense	281300000	USD
CY2020	us-gaap	General And Administrative Expense GeneralAndAdministrativeExpense	391000000.0	USD
CY2019	us-gaap	General And Administrative Expense GeneralAndAdministrativeExpense	379300000	USD
CY2018	us-gaap	General And Administrative Expense GeneralAndAdministrativeExpense	352200000	USD
CY2020	argo	Premium Taxes Boards And Bureaus PremiumTaxesBoardsAndBureaus	29700000	USD
CY2019	argo	Premium Taxes Boards And Bureaus PremiumTaxesBoardsAndBureaus	33000000.0	USD
CY2018	argo	Premium Taxes Boards And Bureaus PremiumTaxesBoardsAndBureaus	32500000	USD
CY2020	argo	Underwriting Acquisition And Insurance Expense Gross UnderwritingAcquisitionAndInsuranceExpenseGross	688700000	USD
CY2019	argo	Underwriting Acquisition And Insurance Expense Gross UnderwritingAcquisitionAndInsuranceExpenseGross	653600000	USD
CY2018	argo	Underwriting Acquisition And Insurance Expense Gross UnderwritingAcquisitionAndInsuranceExpenseGross	666000000.0	USD
CY2020	argo	Net Supplementary Insurance Information Amortization Deferral Of Deferred Policy Acquisition Costs NetSupplementaryInsuranceInformationAmortizationDeferralOfDeferredPolicyAcquisitionCosts	9300000	USD
CY2019	argo	Net Supplementary Insurance Information Amortization Deferral Of Deferred Policy Acquisition Costs NetSupplementaryInsuranceInformationAmortizationDeferralOfDeferredPolicyAcquisitionCosts	-12400000	USD
CY2018	argo	Net Supplementary Insurance Information Amortization Deferral Of Deferred Policy Acquisition Costs NetSupplementaryInsuranceInformationAmortizationDeferralOfDeferredPolicyAcquisitionCosts	9900000	USD
CY2020	argo	Underwriting Acquisition And Insurance Expenses UnderwritingAcquisitionAndInsuranceExpenses	679400000	USD
CY2019	argo	Underwriting Acquisition And Insurance Expenses UnderwritingAcquisitionAndInsuranceExpenses	666000000.0	USD
CY2018	argo	Underwriting Acquisition And Insurance Expenses UnderwritingAcquisitionAndInsuranceExpenses	656100000	USD
CY2020	us-gaap	Other Nonoperating Expense OtherNonoperatingExpense	5800000	USD
CY2019	us-gaap	Other Nonoperating Expense OtherNonoperatingExpense	37600000	USD
CY2020Q2	argo	Other Corporate Expense Civil Penalties OtherCorporateExpenseCivilPenalties	900000	USD
CY2020	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	28000000.0	USD
CY2019	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	37300000	USD
CY2018	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	20800000	USD
CY2020	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	1400000	USD
CY2019	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	1700000	USD
CY2018	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	1400000	USD
CY2020	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	-100000	USD
CY2019	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	-1500000	USD
CY2018	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	3100000	USD
CY2020	argo	Current Income Tax Expense Benefit Other Jurisdictions CurrentIncomeTaxExpenseBenefitOtherJurisdictions	0	USD
CY2019	argo	Current Income Tax Expense Benefit Other Jurisdictions CurrentIncomeTaxExpenseBenefitOtherJurisdictions	100000	USD
CY2018	argo	Current Income Tax Expense Benefit Other Jurisdictions CurrentIncomeTaxExpenseBenefitOtherJurisdictions	100000	USD
CY2020	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	29300000	USD
CY2019	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	37600000	USD
CY2018	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	25400000	USD
CY2020	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-5100000	USD
CY2019	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-17700000	USD
CY2018	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-21600000	USD
CY2020	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	-16600000	USD
CY2019	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	-5800000	USD
CY2018	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	100000	USD
CY2020	argo	Deferred Income Tax Expense Benefit Other Jurisdictions DeferredIncomeTaxExpenseBenefitOtherJurisdictions	100000	USD
CY2019	argo	Deferred Income Tax Expense Benefit Other Jurisdictions DeferredIncomeTaxExpenseBenefitOtherJurisdictions	0	USD
CY2018	argo	Deferred Income Tax Expense Benefit Other Jurisdictions DeferredIncomeTaxExpenseBenefitOtherJurisdictions	100000	USD
CY2020	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-21600000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-23500000	USD
CY2018	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-21400000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	7700000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	14100000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	4000000.0	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	-46400000	USD
CY2020	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	-0.166
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	0	USD
CY2019	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	61000000.0	USD
CY2018	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.066
CY2020	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	4000000.0	USD
CY2019	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	8900000	USD
CY2018	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	7700000	USD
CY2020	us-gaap	Income Tax Reconciliation Tax Exempt Income IncomeTaxReconciliationTaxExemptIncome	700000	USD
CY2019	us-gaap	Income Tax Reconciliation Tax Exempt Income IncomeTaxReconciliationTaxExemptIncome	1200000	USD
CY2018	us-gaap	Income Tax Reconciliation Tax Exempt Income IncomeTaxReconciliationTaxExemptIncome	1900000	USD
CY2020	argo	Income Tax Reconciliation Foreign Exchange Adjustments IncomeTaxReconciliationForeignExchangeAdjustments	1600000	USD
CY2019	argo	Income Tax Reconciliation Foreign Exchange Adjustments IncomeTaxReconciliationForeignExchangeAdjustments	-100000	USD
CY2018	argo	Income Tax Reconciliation Foreign Exchange Adjustments IncomeTaxReconciliationForeignExchangeAdjustments	-600000	USD
CY2020	us-gaap	Income Tax Reconciliation Nondeductible Expense Impairment Losses IncomeTaxReconciliationNondeductibleExpenseImpairmentLosses	1000000.0	USD
CY2019	us-gaap	Income Tax Reconciliation Nondeductible Expense Impairment Losses IncomeTaxReconciliationNondeductibleExpenseImpairmentLosses	2900000	USD
CY2018	us-gaap	Income Tax Reconciliation Nondeductible Expense Impairment Losses IncomeTaxReconciliationNondeductibleExpenseImpairmentLosses	0	USD
CY2020	argo	Income Tax Reconciliation Withholding Taxes IncomeTaxReconciliationWithholdingTaxes	100000	USD
CY2019	argo	Income Tax Reconciliation Withholding Taxes IncomeTaxReconciliationWithholdingTaxes	200000	USD
CY2018	argo	Income Tax Reconciliation Withholding Taxes IncomeTaxReconciliationWithholdingTaxes	400000	USD
CY2020	us-gaap	Income Tax Reconciliation Tax Contingencies IncomeTaxReconciliationTaxContingencies	700000	USD
CY2019	us-gaap	Income Tax Reconciliation Tax Contingencies IncomeTaxReconciliationTaxContingencies	1400000	USD
CY2018	us-gaap	Income Tax Reconciliation Tax Contingencies IncomeTaxReconciliationTaxContingencies	1800000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	144000000.0	USD
CY2019Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	120600000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Unrealized Gains On Trading Securities DeferredTaxLiabilitiesUnrealizedGainsOnTradingSecurities	5700000	USD
CY2020	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	500000	USD
CY2019	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	-1800000	USD
CY2018	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	-1500000	USD
CY2020	us-gaap	Income Tax Reconciliation Change In Enacted Tax Rate IncomeTaxReconciliationChangeInEnactedTaxRate	0	USD
CY2019	us-gaap	Income Tax Reconciliation Change In Enacted Tax Rate IncomeTaxReconciliationChangeInEnactedTaxRate	0	USD
CY2018	us-gaap	Income Tax Reconciliation Change In Enacted Tax Rate IncomeTaxReconciliationChangeInEnactedTaxRate	-800000	USD
CY2020	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	500000	USD
CY2019	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	3800000	USD
CY2018	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	-1100000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	7700000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	14100000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	4000000.0	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Loss Reserves DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsLossReserves	29200000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Loss Reserves DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsLossReserves	24600000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Unearned Premiums Reserve DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsUnearnedPremiumsReserve	25900000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Unearned Premiums Reserve DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsUnearnedPremiumsReserve	25300000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Unrealized Gains On Trading Securities DeferredTaxLiabilitiesUnrealizedGainsOnTradingSecurities	2600000	USD
CY2020Q4	argo	Deferred Tax Liability Unrealized Gains Losses On Fixed Maturities And Other Investment Securities DeferredTaxLiabilityUnrealizedGainsLossesOnFixedMaturitiesAndOtherInvestmentSecurities	22300000	USD
CY2019Q4	argo	Deferred Tax Liability Unrealized Gains Losses On Fixed Maturities And Other Investment Securities DeferredTaxLiabilityUnrealizedGainsLossesOnFixedMaturitiesAndOtherInvestmentSecurities	6100000	USD
CY2020	us-gaap	Unrecognized Tax Benefits Income Tax Penalties Expense UnrecognizedTaxBenefitsIncomeTaxPenaltiesExpense	100000	USD
CY2020Q4	argo	Deferred Tax Liability Unrealized Gains Losses On Limited Partnership Securities DeferredTaxLiabilityUnrealizedGainsLossesOnLimitedPartnershipSecurities	14700000	USD
CY2019Q4	argo	Deferred Tax Liability Unrealized Gains Losses On Limited Partnership Securities DeferredTaxLiabilityUnrealizedGainsLossesOnLimitedPartnershipSecurities	15600000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	20500000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	21600000	USD
CY2020Q4	argo	Deferred Tax Liabilities Acquisition Cost DeferredTaxLiabilitiesAcquisitionCost	20400000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Employee Bonuses DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeBonuses	3800000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost	700000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	27900000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	28300000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Investments DeferredTaxAssetsInvestments	7800000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Investments DeferredTaxAssetsInvestments	10300000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Impairment Losses DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsImpairmentLosses	2000000.0	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Impairment Losses DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsImpairmentLosses	2200000	USD
CY2020Q4	argo	Deferred Tax Assets Rightof Use Assets DeferredTaxAssetsRightofUseAssets	12700000	USD
CY2019Q4	argo	Deferred Tax Assets Rightof Use Assets DeferredTaxAssetsRightofUseAssets	14500000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Employee Bonuses DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeBonuses	6300000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost	1100000	USD
CY2020Q4	argo	Deferred Tax Assets Foreign Underwriting Results DeferredTaxAssetsForeignUnderwritingResults	21900000	USD
CY2019Q4	argo	Deferred Tax Assets Foreign Underwriting Results DeferredTaxAssetsForeignUnderwritingResults	4200000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	9600000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	6300000	USD
CY2019Q4	argo	Deferred Tax Liabilities Acquisition Cost DeferredTaxLiabilitiesAcquisitionCost	18600000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Leasing Arrangements DeferredTaxLiabilitiesLeasingArrangements	11700000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Leasing Arrangements DeferredTaxLiabilitiesLeasingArrangements	14000000.0	USD
CY2020Q4	argo	Deferred Tax Liabilities Tax Cuts And Jobs Act Of2017 Reserve Transitional Liability DeferredTaxLiabilitiesTaxCutsAndJobsActOf2017ReserveTransitionalLiability	2700000	USD
CY2019Q4	argo	Deferred Tax Liabilities Tax Cuts And Jobs Act Of2017 Reserve Transitional Liability DeferredTaxLiabilitiesTaxCutsAndJobsActOf2017ReserveTransitionalLiability	3200000	USD
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CY2018	argo	Payments For Proceeds From Purchases Of Fixed Asset And Other Investing Activities PaymentsForProceedsFromPurchasesOfFixedAssetAndOtherInvestingActivities	32500000	USD
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CY2018	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	31700000	USD
CY2018	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	37500000	USD
CY2018	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-67600000	USD
CY2018	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	-2800000	USD
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CY2017Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	176600000	USD
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CY2020	us-gaap	Supplementary Insurance Information Benefits Claims Losses And Settlement Expense SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense	1208800000	USD
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CY2018	us-gaap	Valuation Allowances And Reserves Deductions ValuationAllowancesAndReservesDeductions	0	USD
CY2018Q4	us-gaap	Valuation Allowances And Reserves Balance ValuationAllowancesAndReservesBalance	29900000	USD
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CY2020Q4	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Discount Deducted From Reserves SupplementalInformationForPropertyCasualtyInsuranceUnderwritersDiscountDeductedFromReserves	17800000	USD
CY2019Q4	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Discount Deducted From Reserves SupplementalInformationForPropertyCasualtyInsuranceUnderwritersDiscountDeductedFromReserves	17900000	USD
CY2018Q4	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Discount Deducted From Reserves SupplementalInformationForPropertyCasualtyInsuranceUnderwritersDiscountDeductedFromReserves	16900000	USD
CY2020Q4	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Unearned Premiums SupplementalInformationForPropertyCasualtyInsuranceUnderwritersUnearnedPremiums	1464800000	USD
CY2019Q4	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Unearned Premiums SupplementalInformationForPropertyCasualtyInsuranceUnderwritersUnearnedPremiums	1410900000	USD
CY2018Q4	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Unearned Premiums SupplementalInformationForPropertyCasualtyInsuranceUnderwritersUnearnedPremiums	1300900000	USD
CY2020	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Earned Premiums SupplementalInformationForPropertyCasualtyInsuranceUnderwritersEarnedPremiums	1780500000	USD
CY2019	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Earned Premiums SupplementalInformationForPropertyCasualtyInsuranceUnderwritersEarnedPremiums	1729700000	USD
CY2018	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Earned Premiums SupplementalInformationForPropertyCasualtyInsuranceUnderwritersEarnedPremiums	1731500000	USD
CY2020	us-gaap	Net Investment Income NetInvestmentIncome	112700000	USD
CY2019	us-gaap	Net Investment Income NetInvestmentIncome	151100000	USD
CY2018	us-gaap	Net Investment Income NetInvestmentIncome	132300000	USD
CY2020	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Current Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersCurrentYearClaimsAndClaimsAdjustmentExpense	1201100000	USD
CY2019	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Current Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersCurrentYearClaimsAndClaimsAdjustmentExpense	1082600000	USD
CY2018	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Current Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersCurrentYearClaimsAndClaimsAdjustmentExpense	1058800000	USD
CY2020	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Prior Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense	7700000	USD
CY2019	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Prior Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense	138100000	USD
CY2018	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Prior Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense	-18000000.0	USD
CY2020	us-gaap	Supplementary Insurance Information Benefits Claims Losses And Settlement Expense SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense	1208800000	USD
CY2019	us-gaap	Supplementary Insurance Information Benefits Claims Losses And Settlement Expense SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense	1220700000	USD
CY2018	us-gaap	Supplementary Insurance Information Benefits Claims Losses And Settlement Expense SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense	1040800000	USD
CY2020	argo	Net Supplementary Insurance Information Amortization Deferral Of Deferred Policy Acquisition Costs NetSupplementaryInsuranceInformationAmortizationDeferralOfDeferredPolicyAcquisitionCosts	9300000	USD
CY2019	argo	Net Supplementary Insurance Information Amortization Deferral Of Deferred Policy Acquisition Costs NetSupplementaryInsuranceInformationAmortizationDeferralOfDeferredPolicyAcquisitionCosts	-12400000	USD
CY2018	argo	Net Supplementary Insurance Information Amortization Deferral Of Deferred Policy Acquisition Costs NetSupplementaryInsuranceInformationAmortizationDeferralOfDeferredPolicyAcquisitionCosts	9900000	USD
CY2020	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Paid Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPaidClaimsAndClaimsAdjustmentExpense	1119800000	USD
CY2019	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Paid Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPaidClaimsAndClaimsAdjustmentExpense	1030300000	USD
CY2018	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Paid Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPaidClaimsAndClaimsAdjustmentExpense	938900000	USD
CY2020	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Premiums Written SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPremiumsWritten	3233300000	USD
CY2019	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Premiums Written SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPremiumsWritten	3130200000	USD

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$ARGD
Argo Group International Holdings, Inc. Stock $argd

2020 Q3 Form 10-K Financial Statement

#000162828021004668 Filed on March 15, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$ARGD Argo Group International Holdings, Inc. Stock $argd

2020 Q3 Form 10-K Financial Statement

#000162828021004668 Filed on March 15, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$ARGD
Argo Group International Holdings, Inc. Stock $argd