$MKL
MARKEL GROUP INC. Stock $mkl

$mkl Overview Financials Valuation SEC Filings Company Website

2020 Q4 Form 10-K Financial Statement

#000109634321000032 Filed on February 19, 2021

Income Statement

Concept	2020 Q4	2019 Q4	2019 Q3
Revenue	$3.356B	$2.582B	$2.033B
YoY Change	29.99%	147.55%	-9.07%
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	$39.00M	$36.00M	$280.6M
YoY Change	8.33%	21.21%	16.04%
% of Gross Profit
Operating Expenses	$2.225B	$1.828B	$1.771B
YoY Change	21.72%	-7.46%	5.39%
Operating Profit			$262.2M
YoY Change			-52.8%
Interest Expense	-$131.5M	-$101.9M	$47.47M
YoY Change	29.05%	-6094.12%	25.04%
% of Operating Profit			18.1%
Other Income/Expense, Net
YoY Change
Pretax Income	$1.013B	$641.0M	$261.9M
YoY Change	58.05%	-168.89%	-49.53%
Income Tax	$165.6M	$129.5M	$57.98M
% Of Pretax Income	16.35%	20.2%	22.13%
Net Earnings	$847.4M	$511.1M	$205.6M
YoY Change	65.8%	-168.01%	-49.78%
Net Earnings / Revenue	25.25%	19.8%	10.11%
Basic Earnings Per Share	$59.44	$36.34	$13.97
Diluted Earnings Per Share	$59.33	$36.26	$13.95
COMMON SHARES
Basic Shares Outstanding	13.78M shares	13.81M shares	13.85M shares
Diluted Shares Outstanding			13.86M shares

Balance Sheet

Concept	2020 Q4	2019 Q4	2019 Q3
SHORT-TERM ASSETS
Cash & Short-Term Investments
YoY Change
Cash & Equivalents	$4.342B	$3.073B	$2.715B
Short-Term Investments
Other Short-Term Assets
YoY Change
Inventory	$412.6M	$303.1M
Prepaid Expenses
Receivables
Other Receivables
Total Short-Term Assets
YoY Change
LONG-TERM ASSETS
Property, Plant & Equipment	$632.0M	$588.6M	$230.0M
YoY Change	7.37%	6.73%
Goodwill	$2.605B	$2.309B	$2.188B
YoY Change	12.83%	3.15%	22.64%
Intangibles	$1.783B	$1.738B	$1.659B
YoY Change	2.54%	0.71%	33.68%
Long-Term Investments	$378.0M	$18.76B	$18.73B
YoY Change	-97.98%	11.38%	1.67%
Other Assets	$875.0M	$428.0M	$484.0M
YoY Change	104.44%	12.04%	72.86%
Total Long-Term Assets
YoY Change
TOTAL ASSETS
Total Short-Term Assets
Total Long-Term Assets
Total Assets	$41.71B	$37.47B	$37.04B
YoY Change	11.3%	12.51%	9.06%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable
YoY Change
Accrued Expenses		$262.0M	$254.0M
YoY Change
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		$262.0M	$254.0M
YoY Change
LONG-TERM LIABILITIES
Long-Term Debt	$3.484B	$3.534B	$3.897B
YoY Change	-1.41%	17.41%	30.2%
Other Long-Term Liabilities	$4.017B	$3.228B	$3.014B
YoY Change	24.44%	15.41%	5.09%
Total Long-Term Liabilities	$7.501B	$6.762B	$6.911B
YoY Change	10.93%	16.45%	17.92%
TOTAL LIABILITIES
Total Short-Term Liabilities		$262.0M	$254.0M
Total Long-Term Liabilities	$7.501B	$6.762B	$6.911B
Total Liabilities	$28.65B	$26.22B	$26.24B
YoY Change	9.28%	9.1%	9.23%
SHAREHOLDERS EQUITY
Retained Earnings	$8.195B	$7.457B	$6.989B
YoY Change	9.9%	28.97%	6.27%
Common Stock	$3.428B	$3.405B	$3.403B
YoY Change	0.69%	0.35%	0.31%
Preferred Stock
YoY Change
Treasury Stock (at cost)
YoY Change
Treasury Stock Shares
Shareholders Equity	$12.80B	$11.07B	$10.62B
YoY Change
Total Liabilities & Shareholders Equity	$41.71B	$37.47B	$37.04B
YoY Change	11.3%	12.51%	9.06%

Cashflow Statement

Concept	2020 Q4	2019 Q4	2019 Q3
OPERATING ACTIVITIES
Net Income	$847.4M	$511.1M	$205.6M
YoY Change	65.8%	-168.01%	-49.78%
Depreciation, Depletion And Amortization	$39.00M	$36.00M	$280.6M
YoY Change	8.33%	21.21%	16.04%
Cash From Operating Activities	$476.0M	$562.1M	$462.8M
YoY Change	-15.32%	333.38%	1.56%
INVESTING ACTIVITIES
Capital Expenditures	-$28.50M	-$27.90M	-$46.30M
YoY Change	2.15%	0.72%	74.72%
Acquisitions
YoY Change
Other Investing Activities	-$505.7M	$149.9M	-$89.30M
YoY Change	-437.36%	-147.39%	-570.0%
Cash From Investing Activities	-$534.2M	$122.0M	-$135.6M
YoY Change	-537.87%	-135.47%	1684.21%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	-41.00M	-411.3M	250.4M
YoY Change	-90.03%	5612.5%	-515.26%
NET CHANGE
Cash From Operating Activities	476.0M	562.1M	462.8M
Cash From Investing Activities	-534.2M	122.0M	-135.6M
Cash From Financing Activities	-41.00M	-411.3M	250.4M
Net Change In Cash	-99.20M	272.8M	577.6M
YoY Change	-136.36%	-223.16%	48.94%
FREE CASH FLOW
Cash From Operating Activities	$476.0M	$562.1M	$462.8M
Capital Expenditures	-$28.50M	-$27.90M	-$46.30M
Free Cash Flow	$504.5M	$590.0M	$509.1M
YoY Change	-14.49%	274.84%	5.58%

Facts In Submission

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CY2020	dei	Document Transition Report DocumentTransitionReport	false
CY2020	dei	Document Period End Date DocumentPeriodEndDate	2020-12-31
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CY2020	dei	Entity Voluntary Filers EntityVoluntaryFilers	No
CY2020	dei	Entity Registrant Name EntityRegistrantName	MARKEL CORPORATION
CY2020	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	VA
CY2020	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	54-1959284
CY2020	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
CY2020	dei	Entity Address City Or Town EntityAddressCityOrTown	Glen Allen
CY2020	dei	Entity Address State Or Province EntityAddressStateOrProvince	VA
CY2020	dei	Entity Interactive Data Current EntityInteractiveDataCurrent	Yes
CY2020	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	23060-6148
CY2020	dei	City Area Code CityAreaCode	804
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CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	2285808000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	-7855000	USD
CY2018	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	-128180000	USD
CY2020	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	356159000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	486346000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	122498000	USD
CY2020	us-gaap	Profit Loss ProfitLoss	831767000	USD
CY2019	us-gaap	Profit Loss ProfitLoss	1799462000	USD
CY2018	us-gaap	Profit Loss ProfitLoss	-130353000	USD
CY2020	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	15737000	USD
CY2019	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	8996000	USD
CY2018	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	-2173000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	816030000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	1790466000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	-128180000	USD
CY2020	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	18400000	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	797630000	USD
CY2019	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	1790466000	USD
CY2019	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	299125000	USD
CY2018	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	-241325000	USD
CY2020	mkl	Reclassification Adjustments For Net Gains Losses Included In Net Income Loss ReclassificationAdjustmentsForNetGainsLossesIncludedInNetIncomeLoss	3386000	USD
CY2019	mkl	Reclassification Adjustments For Net Gains Losses Included In Net Income Loss ReclassificationAdjustmentsForNetGainsLossesIncludedInNetIncomeLoss	1148000	USD
CY2018	mkl	Reclassification Adjustments For Net Gains Losses Included In Net Income Loss ReclassificationAdjustmentsForNetGainsLossesIncludedInNetIncomeLoss	-7849000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	352773000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	297977000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	-233476000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	29847000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	382000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	-16495000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	6998000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-5042000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-2341000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	375622000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	303401000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	2102863000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-247630000	USD
CY2020	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	1207389000	USD
CY2018	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	-377983000	USD
CY2020	us-gaap	Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest	15755000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest	8975000	USD
CY2018	us-gaap	Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest	-2213000	USD
CY2020	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	1191634000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	2093888000	USD
CY2018	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	-375770000	USD
CY2020	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	55.67
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	129.25
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	-9.55
CY2020	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	55.63
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	129.07
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	-9.55
CY2020	us-gaap	Profit Loss ProfitLoss	831767000	USD
CY2019	us-gaap	Profit Loss ProfitLoss	1799462000	USD
CY2018	us-gaap	Profit Loss ProfitLoss	-130353000	USD
CY2020	us-gaap	Increase Decrease In Deferred Income Taxes IncreaseDecreaseInDeferredIncomeTaxes	2733000	USD
CY2019	us-gaap	Increase Decrease In Deferred Income Taxes IncreaseDecreaseInDeferredIncomeTaxes	-323385000	USD
CY2018	us-gaap	Increase Decrease In Deferred Income Taxes IncreaseDecreaseInDeferredIncomeTaxes	-2729000	USD
CY2020	us-gaap	Depreciation Amortization And Accretion Net DepreciationAmortizationAndAccretionNet	307069000	USD
CY2019	us-gaap	Depreciation Amortization And Accretion Net DepreciationAmortizationAndAccretionNet	269239000	USD
CY2018	us-gaap	Depreciation Amortization And Accretion Net DepreciationAmortizationAndAccretionNet	227846000	USD
CY2020	us-gaap	Realized Investment Gains Losses RealizedInvestmentGainsLosses	617979000	USD
CY2019	us-gaap	Realized Investment Gains Losses RealizedInvestmentGainsLosses	1601722000	USD
CY2018	us-gaap	Realized Investment Gains Losses RealizedInvestmentGainsLosses	-437596000	USD
CY2020	us-gaap	Foreign Currency Transaction Gain Loss Realized ForeignCurrencyTransactionGainLossRealized	-95853000	USD
CY2019	us-gaap	Foreign Currency Transaction Gain Loss Realized ForeignCurrencyTransactionGainLossRealized	-2265000	USD
CY2018	us-gaap	Foreign Currency Transaction Gain Loss Realized ForeignCurrencyTransactionGainLossRealized	106598000	USD
CY2020	us-gaap	Goodwill And Intangible Asset Impairment GoodwillAndIntangibleAssetImpairment	0	USD
CY2019	us-gaap	Goodwill And Intangible Asset Impairment GoodwillAndIntangibleAssetImpairment	0	USD
CY2018	us-gaap	Goodwill And Intangible Asset Impairment GoodwillAndIntangibleAssetImpairment	199198000	USD
CY2020	us-gaap	Increase Decrease In Receivables IncreaseDecreaseInReceivables	28174000	USD
CY2019	us-gaap	Increase Decrease In Receivables IncreaseDecreaseInReceivables	103982000	USD
CY2018	us-gaap	Increase Decrease In Receivables IncreaseDecreaseInReceivables	27961000	USD
CY2020	us-gaap	Increase Decrease In Reinsurance Recoverable IncreaseDecreaseInReinsuranceRecoverable	549654000	USD
CY2019	us-gaap	Increase Decrease In Reinsurance Recoverable IncreaseDecreaseInReinsuranceRecoverable	209971000	USD
CY2018	us-gaap	Increase Decrease In Reinsurance Recoverable IncreaseDecreaseInReinsuranceRecoverable	434809000	USD
CY2020	us-gaap	Increase Decrease In Deferred Policy Acquisition Costs IncreaseDecreaseInDeferredPolicyAcquisitionCosts	61569000	USD
CY2019	us-gaap	Increase Decrease In Deferred Policy Acquisition Costs IncreaseDecreaseInDeferredPolicyAcquisitionCosts	93015000	USD
CY2018	us-gaap	Increase Decrease In Deferred Policy Acquisition Costs IncreaseDecreaseInDeferredPolicyAcquisitionCosts	15585000	USD
CY2020	us-gaap	Increase Decrease In Prepaid Reinsurance Premiums IncreaseDecreaseInPrepaidReinsurancePremiums	34480000	USD
CY2019	us-gaap	Increase Decrease In Prepaid Reinsurance Premiums IncreaseDecreaseInPrepaidReinsurancePremiums	84835000	USD
CY2018	us-gaap	Increase Decrease In Prepaid Reinsurance Premiums IncreaseDecreaseInPrepaidReinsurancePremiums	230199000	USD
CY2020	us-gaap	Increase Decrease In Liability For Claims And Claims Adjustment Expense Reserve IncreaseDecreaseInLiabilityForClaimsAndClaimsAdjustmentExpenseReserve	1383430000	USD
CY2019	us-gaap	Increase Decrease In Liability For Claims And Claims Adjustment Expense Reserve IncreaseDecreaseInLiabilityForClaimsAndClaimsAdjustmentExpenseReserve	436234000	USD
CY2018	us-gaap	Increase Decrease In Liability For Claims And Claims Adjustment Expense Reserve IncreaseDecreaseInLiabilityForClaimsAndClaimsAdjustmentExpenseReserve	733605000	USD
CY2020	us-gaap	Increase Decrease In Life Insurance Liabilities IncreaseDecreaseInLifeInsuranceLiabilities	-44651000	USD
CY2019	us-gaap	Increase Decrease In Life Insurance Liabilities IncreaseDecreaseInLifeInsuranceLiabilities	-52159000	USD
CY2018	us-gaap	Increase Decrease In Life Insurance Liabilities IncreaseDecreaseInLifeInsuranceLiabilities	-50541000	USD
CY2020	us-gaap	Increase Decrease In Unearned Premiums IncreaseDecreaseInUnearnedPremiums	354679000	USD
CY2019	us-gaap	Increase Decrease In Unearned Premiums IncreaseDecreaseInUnearnedPremiums	438951000	USD
CY2018	us-gaap	Increase Decrease In Unearned Premiums IncreaseDecreaseInUnearnedPremiums	293078000	USD
CY2020	us-gaap	Increase Decrease In Reinsurance Payables IncreaseDecreaseInReinsurancePayables	76586000	USD
CY2019	us-gaap	Increase Decrease In Reinsurance Payables IncreaseDecreaseInReinsurancePayables	65460000	USD
CY2018	us-gaap	Increase Decrease In Reinsurance Payables IncreaseDecreaseInReinsurancePayables	-4313000	USD
CY2020	us-gaap	Increase Decrease In Accrued Income Taxes Payable IncreaseDecreaseInAccruedIncomeTaxesPayable	-70277000	USD
CY2019	us-gaap	Increase Decrease In Accrued Income Taxes Payable IncreaseDecreaseInAccruedIncomeTaxesPayable	36938000	USD
CY2018	us-gaap	Increase Decrease In Accrued Income Taxes Payable IncreaseDecreaseInAccruedIncomeTaxesPayable	53730000	USD
CY2020	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	-97720000	USD
CY2019	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	-47870000	USD
CY2018	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	54566000	USD
CY2020	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	1737587000	USD
CY2019	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	1274120000	USD
CY2018	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	892857000	USD
CY2020	us-gaap	Proceeds From Sale Maturity And Collections Of Investments ProceedsFromSaleMaturityAndCollectionsOfInvestments	1580288000	USD
CY2019	us-gaap	Proceeds From Sale Maturity And Collections Of Investments ProceedsFromSaleMaturityAndCollectionsOfInvestments	353918000	USD
CY2018	us-gaap	Proceeds From Sale Maturity And Collections Of Investments ProceedsFromSaleMaturityAndCollectionsOfInvestments	419199000	USD
CY2020	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	642135000	USD
CY2019	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	772336000	USD
CY2018	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	551808000	USD
CY2020	us-gaap	Payments To Acquire Investments PaymentsToAcquireInvestments	1322218000	USD
CY2019	us-gaap	Payments To Acquire Investments PaymentsToAcquireInvestments	955970000	USD
CY2018	us-gaap	Payments To Acquire Investments PaymentsToAcquireInvestments	1545913000	USD
CY2020	us-gaap	Payments For Proceeds From Short Term Investments PaymentsForProceedsFromShortTermInvestments	829457000	USD
CY2019	us-gaap	Payments For Proceeds From Short Term Investments PaymentsForProceedsFromShortTermInvestments	95867000	USD
CY2018	us-gaap	Payments For Proceeds From Short Term Investments PaymentsForProceedsFromShortTermInvestments	-1101636000	USD
CY2020	us-gaap	Payments To Acquire Equity Method Investments PaymentsToAcquireEquityMethodInvestments	5066000	USD
CY2019	us-gaap	Payments To Acquire Equity Method Investments PaymentsToAcquireEquityMethodInvestments	257663000	USD
CY2018	us-gaap	Payments To Acquire Equity Method Investments PaymentsToAcquireEquityMethodInvestments	8864000	USD
CY2020	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	101301000	USD
CY2019	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	123376000	USD
CY2018	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	106593000	USD
CY2020	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	554127000	USD
CY2019	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	245332000	USD
CY2018	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	1175211000	USD
CY2020	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-77998000	USD
CY2019	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-16795000	USD
CY2018	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	33301000	USD
CY2020	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-511748000	USD
CY2019	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-535159000	USD
CY2018	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-797239000	USD
CY2020	us-gaap	Proceeds From Issuance Of Debt ProceedsFromIssuanceOfDebt	223183000	USD
CY2019	us-gaap	Proceeds From Issuance Of Debt ProceedsFromIssuanceOfDebt	1645182000	USD
CY2018	us-gaap	Proceeds From Issuance Of Preferred Stock And Preference Stock ProceedsFromIssuanceOfPreferredStockAndPreferenceStock	0	USD
CY2018	us-gaap	Proceeds From Issuance Of Debt ProceedsFromIssuanceOfDebt	206949000	USD
CY2020	us-gaap	Repayments Of Debt RepaymentsOfDebt	275996000	USD
CY2019	us-gaap	Repayments Of Debt RepaymentsOfDebt	1103674000	USD
CY2018	us-gaap	Repayments Of Debt RepaymentsOfDebt	289199000	USD
CY2020	us-gaap	Payments Of Debt Extinguishment Costs PaymentsOfDebtExtinguishmentCosts	0	USD
CY2019	us-gaap	Payments Of Debt Extinguishment Costs PaymentsOfDebtExtinguishmentCosts	27073000	USD
CY2018	us-gaap	Payments Of Debt Extinguishment Costs PaymentsOfDebtExtinguishmentCosts	0	USD
CY2020	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	26832000	USD
CY2019	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	116307000	USD
CY2018	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	54007000	USD
CY2020	us-gaap	Proceeds From Issuance Of Preferred Stock And Preference Stock ProceedsFromIssuanceOfPreferredStockAndPreferenceStock	591891000	USD
CY2019	us-gaap	Proceeds From Issuance Of Preferred Stock And Preference Stock ProceedsFromIssuanceOfPreferredStockAndPreferenceStock	0	USD
CY2020	us-gaap	Payments Of Dividends Preferred Stock And Preference Stock PaymentsOfDividendsPreferredStockAndPreferenceStock	18400000	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	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	-59290000	USD
CY2019	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	-38811000	USD
CY2018	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	-42728000	USD
CY2020	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	434556000	USD
CY2019	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	359317000	USD
CY2018	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-178985000	USD
CY2020	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	55901000	USD
CY2019	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	5643000	USD
CY2018	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	-21047000	USD
CY2020	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	1716296000	USD
CY2019	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	1103921000	USD
CY2018	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-104414000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	3500353000	USD
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	2396432000	USD
CY2017Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	2500846000	USD
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	5216649000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	3500353000	USD
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	2396432000	USD
CY2020	us-gaap	Use Of Estimates UseOfEstimates	Use of Estimates. The preparation of financial statements in accordance with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingent assets and liabilities. Management periodically reviews its estimates and assumptions. Quarterly reviews include evaluating the adequacy of reserves for unpaid losses and loss adjustment expenses, life and annuity reinsurance benefit reserves and contingencies. Estimates and assumptions for goodwill and intangible assets are reviewed in conjunction with an acquisition, and goodwill and indefinite-lived intangible assets are reassessed at least annually for impairment. Actual results may differ materially from the estimates and assumptions used in preparing the consolidated financial statements.
CY2020Q4	us-gaap	Allowance For Doubtful Accounts Receivable AllowanceForDoubtfulAccountsReceivable	24200000	USD
CY2019Q4	us-gaap	Allowance For Doubtful Accounts Receivable AllowanceForDoubtfulAccountsReceivable	18700000	USD
CY2020Q4	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	28400000	USD
CY2019Q4	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	26800000	USD
CY2020	mkl	Deferred Policy Acquisition Cost Amortization Period DeferredPolicyAcquisitionCostAmortizationPeriod	P1Y
CY2020Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	632000000.0	USD
CY2019Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	588600000	USD
CY2020Q4	us-gaap	Inventory Net InventoryNet	412600000	USD
CY2019Q4	us-gaap	Inventory Net InventoryNet	303100000	USD
CY2020	mkl	Tax Benefit Greater Than Fifty Percent TaxBenefitGreaterThanFiftyPercent	0.50
CY2020	mkl	Revenue Recognition Period Insurance Premiums RevenueRecognitionPeriodInsurancePremiums	P1Y
CY2020	mkl	Reinsurance Accounting Policy For Program Services ReinsuranceAccountingPolicyForProgramServices	Program Services. In connection with its program services business, the Company enters into contractual agreements with both producing general agents and reinsurers, whereby the general agents and reinsurers are typically obligated to each other for payment of insurance amounts, including premiums, commissions and losses. To the extent these funds are not the obligation of the Company and are settled directly between the general agent and the reinsurer, no receivables or payables are recorded for these amounts. All obligations of the Company's insurance subsidiaries owed to or on behalf of their policyholders are recorded by the Company and, to the extent appropriate, offsetting reinsurance recoverables are recorded.
CY2020	us-gaap	Premiums Written Gross PremiumsWrittenGross	9266665000	USD
CY2020	us-gaap	Premiums Written Net PremiumsWrittenNet	5932238000	USD
CY2020	us-gaap	Premiums Earned Net PremiumsEarnedNet	5612205000	USD
CY2020	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Current Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersCurrentYearClaimsAndClaimsAdjustmentExpense	4073325000	USD
CY2020	mkl	Supplemental Info For Property Casualty Insurance Underwriters Prior Year Claims And Claims Adjustment Expense Including Amounts Related To Liabilities Not Included In Unpaid Losses And Lae SupplementalInfoForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpenseIncludingAmountsRelatedToLiabilitiesNotIncludedInUnpaidLossesAndLAE	-606364000	USD
CY2020	us-gaap	Deferred Policy Acquisition Cost Amortization Expense DeferredPolicyAcquisitionCostAmortizationExpense	1229161000	USD
CY2020	us-gaap	Other Underwriting Expense OtherUnderwritingExpense	788466000	USD
CY2020	mkl	Underwriting Profit Loss UnderwritingProfitLoss	127617000	USD
CY2020	us-gaap	Net Investment Income NetInvestmentIncome	371830000	USD
CY2020	mkl	Net Investment Gains Losses NetInvestmentGainsLosses	617979000	USD
CY2020	mkl	Products Revenues ProductsRevenues	1439515000	USD
CY2020	mkl	Servicesandotherrevenues Servicesandotherrevenues	1693537000	USD
CY2020	mkl	Productsexpenses Productsexpenses	1256159000	USD
CY2020	mkl	Servicesandotherexpenses Servicesandotherexpenses	1561120000	USD
CY2020	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	159315000	USD
CY2020	mkl	Total Profit Loss TotalProfitLoss	1273884000	USD
CY2020	us-gaap	Interest Expense InterestExpense	177582000	USD
CY2020	us-gaap	Foreign Currency Transaction Gain Loss Realized ForeignCurrencyTransactionGainLossRealized	-95853000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	1000449000	USD
CY2020	us-gaap	Combined Ratio CombinedRatio	0.98
CY2019	us-gaap	Premiums Written Gross PremiumsWrittenGross	8779971000	USD
CY2019	us-gaap	Premiums Written Net PremiumsWrittenNet	5412071000	USD
CY2019	us-gaap	Premiums Earned Net PremiumsEarnedNet	5049793000	USD
CY2019	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Current Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersCurrentYearClaimsAndClaimsAdjustmentExpense	3426441000	USD
CY2019	mkl	Supplemental Info For Property Casualty Insurance Underwriters Prior Year Claims And Claims Adjustment Expense Including Amounts Related To Liabilities Not Included In Unpaid Losses And Lae SupplementalInfoForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpenseIncludingAmountsRelatedToLiabilitiesNotIncludedInUnpaidLossesAndLAE	-535251000	USD
CY2019	us-gaap	Deferred Policy Acquisition Cost Amortization Expense DeferredPolicyAcquisitionCostAmortizationExpense	1100496000	USD
CY2019	us-gaap	Other Underwriting Expense OtherUnderwritingExpense	777597000	USD
CY2019	mkl	Underwriting Profit Loss UnderwritingProfitLoss	280510000	USD
CY2019	us-gaap	Net Investment Income NetInvestmentIncome	451888000	USD
CY2019	mkl	Net Investment Gains Losses NetInvestmentGainsLosses	1601722000	USD
CY2019	mkl	Products Revenues ProductsRevenues	1609586000	USD
CY2019	mkl	Servicesandotherrevenues Servicesandotherrevenues	813202000	USD
CY2019	mkl	Productsexpenses Productsexpenses	1455245000	USD
CY2019	mkl	Servicesandotherexpenses Servicesandotherexpenses	675679000	USD
CY2019	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	148638000	USD
CY2019	mkl	Total Profit Loss TotalProfitLoss	2477346000	USD
CY2019	us-gaap	Interest Expense InterestExpense	171687000	USD
CY2019	us-gaap	Foreign Currency Transaction Gain Loss Realized ForeignCurrencyTransactionGainLossRealized	-2265000	USD
CY2019	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-17586000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	2285808000	USD
CY2019	us-gaap	Combined Ratio CombinedRatio	0.94
CY2018	us-gaap	Premiums Written Gross PremiumsWrittenGross	7864469000	USD
CY2018	us-gaap	Premiums Written Net PremiumsWrittenNet	4787578000	USD
CY2018	us-gaap	Premiums Earned Net PremiumsEarnedNet	4712060000	USD
CY2018	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Current Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersCurrentYearClaimsAndClaimsAdjustmentExpense	3371699000	USD
CY2018	mkl	Supplemental Info For Property Casualty Insurance Underwriters Prior Year Claims And Claims Adjustment Expense Including Amounts Related To Liabilities Not Included In Unpaid Losses And Lae SupplementalInfoForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpenseIncludingAmountsRelatedToLiabilitiesNotIncludedInUnpaidLossesAndLAE	-550984000	USD
CY2018	us-gaap	Deferred Policy Acquisition Cost Amortization Expense DeferredPolicyAcquisitionCostAmortizationExpense	1009303000	USD
CY2018	us-gaap	Other Underwriting Expense OtherUnderwritingExpense	768208000	USD
CY2018	mkl	Underwriting Profit Loss UnderwritingProfitLoss	113834000	USD
CY2018	us-gaap	Net Investment Income NetInvestmentIncome	434215000	USD
CY2018	mkl	Net Investment Gains Losses NetInvestmentGainsLosses	-437596000	USD
CY2018	mkl	Products Revenues ProductsRevenues	1497523000	USD
CY2018	mkl	Servicesandotherrevenues Servicesandotherrevenues	635083000	USD
CY2018	mkl	Productsexpenses Productsexpenses	1413248000	USD
CY2018	mkl	Servicesandotherexpenses Servicesandotherexpenses	474924000	USD
CY2018	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	115930000	USD
CY2018	us-gaap	Goodwill And Intangible Asset Impairment GoodwillAndIntangibleAssetImpairment	199198000	USD
CY2018	mkl	Total Profit Loss TotalProfitLoss	39759000	USD
CY2020Q4	us-gaap	Liability For Claims And Claims Adjustment Expense LiabilityForClaimsAndClaimsAdjustmentExpense	16222376000	USD
CY2019Q4	us-gaap	Deferred Policy Acquisition Costs DeferredPolicyAcquisitionCosts	566042000	USD
CY2018	us-gaap	Interest Expense InterestExpense	154212000	USD
CY2018	us-gaap	Foreign Currency Transaction Gain Loss Realized ForeignCurrencyTransactionGainLossRealized	106598000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	-7855000	USD
CY2018	us-gaap	Combined Ratio CombinedRatio	0.98
CY2020	us-gaap	Premiums Earned Net PremiumsEarnedNet	5612205000	USD
CY2019	us-gaap	Premiums Earned Net PremiumsEarnedNet	5049793000	USD
CY2018	us-gaap	Premiums Earned Net PremiumsEarnedNet	4712060000	USD
CY2020Q4	us-gaap	Assets Assets	41710054000	USD
CY2019Q4	us-gaap	Assets Assets	37473815000	USD
CY2020Q4	us-gaap	Deferred Policy Acquisition Costs DeferredPolicyAcquisitionCosts	630794000	USD
CY2020Q4	us-gaap	Unearned Premiums UnearnedPremiums	4433245000	USD
CY2019Q4	us-gaap	Unearned Premiums UnearnedPremiums	4057727000	USD
CY2019Q4	us-gaap	Liability For Claims And Claims Adjustment Expense LiabilityForClaimsAndClaimsAdjustmentExpense	14728676000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	9655261000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	9655261000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	1027430000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	957000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	10681734000	USD
CY2020Q4	mkl	Shortterm Investments Availablefor Sale Amortized Cost Basis ShorttermInvestmentsAvailableforSaleAmortizedCostBasis	2030460000	USD
CY2020Q4	mkl	Shortterm Investments Availablefor Sale Accumulated Gross Unrealized Gain Before Tax ShorttermInvestmentsAvailableforSaleAccumulatedGrossUnrealizedGainBeforeTax	3645000	USD
CY2020Q4	mkl	Shortterm Investments Availablefor Sale Accumulated Gross Unrealized Loss Before Tax ShorttermInvestmentsAvailableforSaleAccumulatedGrossUnrealizedLossBeforeTax	6000	USD
CY2020Q4	mkl	Shortterm Investments Availablefor Sale ShorttermInvestmentsAvailableforSale	2034099000	USD
CY2020Q4	mkl	Investments Availablefor Sale Amortized Cost Basis InvestmentsAvailableforSaleAmortizedCostBasis	11685721000	USD
CY2020Q4	mkl	Investments Availablefor Sale Accumulated Gross Unrealized Gain Before Tax InvestmentsAvailableforSaleAccumulatedGrossUnrealizedGainBeforeTax	1031075000	USD
CY2020Q4	mkl	Investments Availablefor Sale Accumulated Gross Unrealized Loss Before Tax InvestmentsAvailableforSaleAccumulatedGrossUnrealizedLossBeforeTax	963000	USD
CY2020Q4	mkl	Investments Availablefor Sale InvestmentsAvailableforSale	12715833000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	9448840000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	9448840000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	536488000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	14419000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	9970909000	USD
CY2019Q4	mkl	Shortterm Investments Availablefor Sale Amortized Cost Basis ShorttermInvestmentsAvailableforSaleAmortizedCostBasis	1194953000	USD
CY2019Q4	mkl	Shortterm Investments Availablefor Sale Accumulated Gross Unrealized Gain Before Tax ShorttermInvestmentsAvailableforSaleAccumulatedGrossUnrealizedGainBeforeTax	1355000	USD
CY2019Q4	mkl	Shortterm Investments Availablefor Sale Accumulated Gross Unrealized Loss Before Tax ShorttermInvestmentsAvailableforSaleAccumulatedGrossUnrealizedLossBeforeTax	60000	USD
CY2019Q4	mkl	Shortterm Investments Availablefor Sale ShorttermInvestmentsAvailableforSale	1196248000	USD
CY2019Q4	mkl	Investments Availablefor Sale Amortized Cost Basis InvestmentsAvailableforSaleAmortizedCostBasis	10643793000	USD
CY2019Q4	mkl	Investments Availablefor Sale Accumulated Gross Unrealized Gain Before Tax InvestmentsAvailableforSaleAccumulatedGrossUnrealizedGainBeforeTax	537843000	USD
CY2019Q4	mkl	Investments Availablefor Sale Accumulated Gross Unrealized Loss Before Tax InvestmentsAvailableforSaleAccumulatedGrossUnrealizedLossBeforeTax	14479000	USD
CY2019Q4	mkl	Investments Availablefor Sale InvestmentsAvailableforSale	11167157000	USD
CY2020Q4	mkl	Shortterm Investments Availableforsale Continuous Unrealized Loss Position Lessthan12 Months ShorttermInvestmentsAvailableforsaleContinuousUnrealizedLossPositionLessthan12Months	349978000	USD
CY2020Q4	mkl	Shortterm Investments Availableforsale Continuous Unrealized Loss Position Lessthan12 Months Accumulated Loss ShorttermInvestmentsAvailableforsaleContinuousUnrealizedLossPositionLessthan12MonthsAccumulatedLoss	6000	USD
CY2020Q4	mkl	Shortterm Investments Availableforsale Continuous Unrealized Loss Position12 Monthsor Longer ShorttermInvestmentsAvailableforsaleContinuousUnrealizedLossPosition12MonthsorLonger	0	USD
CY2020Q4	mkl	Shortterm Investments Availableforsale Continuous Unrealized Loss Position12 Monthsor Longer Accumulated Loss ShorttermInvestmentsAvailableforsaleContinuousUnrealizedLossPosition12MonthsorLongerAccumulatedLoss	0	USD
CY2020Q4	mkl	Shortterm Investments Availableforsale Unrealized Loss Position Total ShorttermInvestmentsAvailableforsaleUnrealizedLossPositionTotal	349978000	USD
CY2020Q4	mkl	Shortterm Investments Availableforsale Unrealized Loss Position Accumulated Loss ShorttermInvestmentsAvailableforsaleUnrealizedLossPositionAccumulatedLoss	6000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months	496518000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	943000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger	5486000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	20000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position DebtSecuritiesAvailableForSaleUnrealizedLossPosition	502004000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Accumulated Loss DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss	963000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Number Of Positions DebtSecuritiesAvailableForSaleUnrealizedLossPositionNumberOfPositions	36	securities
CY2020Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position DebtSecuritiesAvailableForSaleUnrealizedLossPosition	502000000.0	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Accumulated Loss DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss	963000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Number Of Positions DebtSecuritiesAvailableForSaleUnrealizedLossPositionNumberOfPositions	36	securities
CY2020Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer Number Of Positions DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerNumberOfPositions	6	securities
CY2020Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger	5500000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	20000	USD
CY2019Q4	mkl	Shortterm Investments Availableforsale Continuous Unrealized Loss Position Lessthan12 Months ShorttermInvestmentsAvailableforsaleContinuousUnrealizedLossPositionLessthan12Months	3316000	USD
CY2019Q4	mkl	Shortterm Investments Availableforsale Continuous Unrealized Loss Position Lessthan12 Months Accumulated Loss ShorttermInvestmentsAvailableforsaleContinuousUnrealizedLossPositionLessthan12MonthsAccumulatedLoss	60000	USD
CY2019Q4	mkl	Shortterm Investments Availableforsale Continuous Unrealized Loss Position12 Monthsor Longer ShorttermInvestmentsAvailableforsaleContinuousUnrealizedLossPosition12MonthsorLonger	0	USD
CY2019Q4	mkl	Shortterm Investments Availableforsale Continuous Unrealized Loss Position12 Monthsor Longer Accumulated Loss ShorttermInvestmentsAvailableforsaleContinuousUnrealizedLossPosition12MonthsorLongerAccumulatedLoss	0	USD
CY2019Q4	mkl	Shortterm Investments Availableforsale Unrealized Loss Position Total ShorttermInvestmentsAvailableforsaleUnrealizedLossPositionTotal	3316000	USD
CY2019Q4	mkl	Shortterm Investments Availableforsale Unrealized Loss Position Accumulated Loss ShorttermInvestmentsAvailableforsaleUnrealizedLossPositionAccumulatedLoss	60000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months	611152000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	7192000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger	352025000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	7287000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position DebtSecuritiesAvailableForSaleUnrealizedLossPosition	963177000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Accumulated Loss DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss	14479000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Number Of Positions DebtSecuritiesAvailableForSaleUnrealizedLossPositionNumberOfPositions	201	securities
CY2019Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position DebtSecuritiesAvailableForSaleUnrealizedLossPosition	963200000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Accumulated Loss DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss	14500000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Number Of Positions DebtSecuritiesAvailableForSaleUnrealizedLossPositionNumberOfPositions	201	securities
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer Number Of Positions DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerNumberOfPositions	122	securities
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger	352000000.0	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	7300000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities Within One Year Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost	383330000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities Within One Year Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue	390636000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost	1861527000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	1994002000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost	2348671000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	2592111000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost	2507932000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue	2942992000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities Single Maturity Date Amortized Cost Basis AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis	7101460000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities Single Maturity Date AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDate	7919741000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	9655261000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	10681734000	USD
CY2020	mkl	Estimated Average Duration Of Fixed Maturities EstimatedAverageDurationOfFixedMaturities	P5Y7M6D
CY2020	us-gaap	Interest Income Securities Tax Exempt InterestIncomeSecuritiesTaxExempt	63718000	USD
CY2019	us-gaap	Interest Income Securities Tax Exempt InterestIncomeSecuritiesTaxExempt	71351000	USD
CY2018	us-gaap	Interest Income Securities Tax Exempt InterestIncomeSecuritiesTaxExempt	80016000	USD
CY2020	us-gaap	Interest Income Deposits With Financial Institutions InterestIncomeDepositsWithFinancialInstitutions	14321000	USD
CY2019	us-gaap	Interest Income Deposits With Financial Institutions InterestIncomeDepositsWithFinancialInstitutions	50425000	USD
CY2018	us-gaap	Interest Income Deposits With Financial Institutions InterestIncomeDepositsWithFinancialInstitutions	48765000	USD
CY2020	us-gaap	Investment Income Dividend InvestmentIncomeDividend	89303000	USD
CY2019	us-gaap	Investment Income Dividend InvestmentIncomeDividend	100222000	USD
CY2018	us-gaap	Investment Income Dividend InvestmentIncomeDividend	90840000	USD
CY2020	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	-4430000	USD
CY2019	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	4368000	USD
CY2018	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	-1924000	USD
CY2020	us-gaap	Other Interest And Dividend Income OtherInterestAndDividendIncome	434000	USD
CY2019	us-gaap	Other Interest And Dividend Income OtherInterestAndDividendIncome	5338000	USD
CY2018	us-gaap	Other Interest And Dividend Income OtherInterestAndDividendIncome	881000	USD
CY2020	us-gaap	Investment Income Interest And Dividend InvestmentIncomeInterestAndDividend	388049000	USD
CY2019	us-gaap	Investment Income Interest And Dividend InvestmentIncomeInterestAndDividend	467383000	USD
CY2018	us-gaap	Investment Income Interest And Dividend InvestmentIncomeInterestAndDividend	450965000	USD
CY2020	us-gaap	Investment Income Investment Expense InvestmentIncomeInvestmentExpense	16219000	USD
CY2019	us-gaap	Investment Income Investment Expense InvestmentIncomeInvestmentExpense	15495000	USD
CY2018	us-gaap	Investment Income Investment Expense InvestmentIncomeInvestmentExpense	16750000	USD
CY2020	us-gaap	Net Investment Income NetInvestmentIncome	371830000	USD
CY2019	us-gaap	Net Investment Income NetInvestmentIncome	451888000	USD
CY2018	us-gaap	Net Investment Income NetInvestmentIncome	434215000	USD
CY2020	us-gaap	Debt Securities Available For Sale Realized Gain Loss DebtSecuritiesAvailableForSaleRealizedGainLoss	14780000	USD
CY2019	us-gaap	Debt Securities Available For Sale Realized Gain Loss DebtSecuritiesAvailableForSaleRealizedGainLoss	-1482000	USD
CY2018	us-gaap	Debt Securities Available For Sale Realized Gain Loss DebtSecuritiesAvailableForSaleRealizedGainLoss	-11974000	USD
CY2020	us-gaap	Equity Securities Fv Ni Realized Gain Loss EquitySecuritiesFvNiRealizedGainLoss	-470008000	USD
CY2019	us-gaap	Equity Securities Fv Ni Realized Gain Loss EquitySecuritiesFvNiRealizedGainLoss	38291000	USD
CY2018	us-gaap	Equity Securities Fv Ni Realized Gain Loss EquitySecuritiesFvNiRealizedGainLoss	20177000	USD
CY2020	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	1073207000	USD
CY2019	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	1564913000	USD
CY2018	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	-445799000	USD
CY2020	us-gaap	Equity Securities Fv Ni Gain Loss EquitySecuritiesFvNiGainLoss	603199000	USD
CY2019	us-gaap	Equity Securities Fv Ni Gain Loss EquitySecuritiesFvNiGainLoss	1603204000	USD
CY2018	us-gaap	Equity Securities Fv Ni Gain Loss EquitySecuritiesFvNiGainLoss	-425622000	USD
CY2020	mkl	Net Investment Gains Losses NetInvestmentGainsLosses	617979000	USD
CY2019	mkl	Net Investment Gains Losses NetInvestmentGainsLosses	1601722000	USD
CY2018	mkl	Net Investment Gains Losses NetInvestmentGainsLosses	-437596000	USD
CY2020	mkl	Other Comprehensive Income Securities Availablefor Sale Lifeand Annuity Benefits Reserves Adjustmentbefore Tax OtherComprehensiveIncomeSecuritiesAvailableforSaleLifeandAnnuityBenefitsReservesAdjustmentbeforeTax	-68158000	USD
CY2019	mkl	Other Comprehensive Income Securities Availablefor Sale Lifeand Annuity Benefits Reserves Adjustmentbefore Tax OtherComprehensiveIncomeSecuritiesAvailableforSaleLifeandAnnuityBenefitsReservesAdjustmentbeforeTax	-51390000	USD
CY2018	mkl	Other Comprehensive Income Securities Availablefor Sale Lifeand Annuity Benefits Reserves Adjustmentbefore Tax OtherComprehensiveIncomeSecuritiesAvailableforSaleLifeandAnnuityBenefitsReservesAdjustmentbeforeTax	0	USD
CY2020	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Before Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax	442089000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Before Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax	381890000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Before Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax	-299446000	USD
CY2020Q4	mkl	Restricted Investments Available For Sale RestrictedInvestmentsAvailableForSale	4217230000	USD
CY2019Q4	mkl	Restricted Investments Available For Sale RestrictedInvestmentsAvailableForSale	4134164000	USD
CY2020Q4	us-gaap	Restricted Cash And Cash Equivalents RestrictedCashAndCashEquivalents	874913000	USD
CY2019Q4	us-gaap	Restricted Cash And Cash Equivalents RestrictedCashAndCashEquivalents	427546000	USD
CY2020Q4	us-gaap	Restricted Cash And Investments RestrictedCashAndInvestments	5092143000	USD
CY2019Q4	us-gaap	Restricted Cash And Investments RestrictedCashAndInvestments	4561710000	USD
CY2020Q4	us-gaap	Restricted Cash And Investments RestrictedCashAndInvestments	5092143000	USD
CY2019Q4	us-gaap	Restricted Cash And Investments RestrictedCashAndInvestments	4561710000	USD
CY2020	mkl	Percentage Threshold Of Shareholders Equity Used To Define Concentration Of Investments PercentageThresholdOfShareholdersEquityUsedToDefineConcentrationOfInvestments	0.10
CY2019Q4	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Value FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue	45992000	USD
CY2018Q4	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Value FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue	53728000	USD
CY2020	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Purchases FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases	90000000	USD
CY2019	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Purchases FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases	500000	USD
CY2020	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Sales FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales	73902000	USD
CY2019	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Sales FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales	9448000	USD
CY2020	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Gain Loss Included In Earnings1 FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1	-3597000	USD
CY2019	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Gain Loss Included In Earnings1 FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1	1212000	USD
CY2020Q4	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Value FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue	58493000	USD
CY2019Q4	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Value FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue	45992000	USD
CY2020Q1	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Purchases FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases	90000000.0	USD
CY2018Q4	us-gaap	Goodwill Goodwill	2237975000	USD
CY2019	us-gaap	Goodwill Acquired During Period GoodwillAcquiredDuringPeriod	118878000	USD
CY2019	us-gaap	Goodwill Foreign Currency Translation Gain Loss GoodwillForeignCurrencyTranslationGainLoss	-48305000	USD
CY2019Q4	us-gaap	Goodwill Goodwill	2308548000	USD
CY2020	us-gaap	Goodwill Acquired During Period GoodwillAcquiredDuringPeriod	287097000	USD
CY2020	us-gaap	Goodwill Foreign Currency Translation Gain Loss GoodwillForeignCurrencyTranslationGainLoss	8979000	USD
CY2020Q4	us-gaap	Goodwill Goodwill	2604624000	USD
CY2020Q4	us-gaap	Goodwill Impaired Accumulated Impairment Loss GoodwillImpairedAccumulatedImpairmentLoss	139200000	USD
CY2020	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	USD
CY2018Q4	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	1726196000	USD
CY2019	mkl	Intangible Assets Acquired During Period IntangibleAssetsAcquiredDuringPeriod	113135000	USD
CY2019	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	148638000	USD
CY2019	us-gaap	Finite Lived Intangible Assets Translation And Purchase Accounting Adjustments FiniteLivedIntangibleAssetsTranslationAndPurchaseAccountingAdjustments	47781000	USD
CY2019Q4	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	1738474000	USD
CY2020	mkl	Intangible Assets Acquired During Period IntangibleAssetsAcquiredDuringPeriod	210000000	USD
CY2020	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	159315000	USD
CY2020	us-gaap	Finite Lived Intangible Assets Translation And Purchase Accounting Adjustments FiniteLivedIntangibleAssetsTranslationAndPurchaseAccountingAdjustments	-6441000	USD
CY2020Q4	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	1782718000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Next Twelve Months FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths	159000000.0	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Two FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo	155500000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Three FiniteLivedIntangibleAssetsAmortizationExpenseYearThree	153700000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Four FiniteLivedIntangibleAssetsAmortizationExpenseYearFour	151700000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Five FiniteLivedIntangibleAssetsAmortizationExpenseYearFive	145100000	USD
CY2020Q4	us-gaap	Indefinite Lived Intangible Assets Excluding Goodwill IndefiniteLivedIntangibleAssetsExcludingGoodwill	92400000	USD
CY2020	mkl	Intangible Assets Acquired During Period IntangibleAssetsAcquiredDuringPeriod	210000000.0	USD
CY2020	us-gaap	Acquired Finite Lived Intangible Assets Weighted Average Useful Life AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife	P16Y
CY2020Q4	us-gaap	Intangible Assets Gross Excluding Goodwill IntangibleAssetsGrossExcludingGoodwill	2563284000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Accumulated Amortization FiniteLivedIntangibleAssetsAccumulatedAmortization	780566000	USD
CY2019Q4	us-gaap	Intangible Assets Gross Excluding Goodwill IntangibleAssetsGrossExcludingGoodwill	2358086000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Accumulated Amortization FiniteLivedIntangibleAssetsAccumulatedAmortization	619612000	USD
CY2020	mkl	Lease Of Facilities And Furniture Maximum Duration LeaseOfFacilitiesAndFurnitureMaximumDuration	P22Y
CY2020	us-gaap	Operating Lease Cost OperatingLeaseCost	94400000	USD
CY2019	us-gaap	Operating Leases Rent Expense Net OperatingLeasesRentExpenseNet	62700000	USD
CY2018	us-gaap	Operating Leases Rent Expense Net OperatingLeasesRentExpenseNet	52900000	USD
CY2020Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P12Y1M6D
CY2019Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P8Y6M
CY2020Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.030
CY2019Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.033
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Next Twelve Months LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths	90311000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Two LesseeOperatingLeaseLiabilityPaymentsDueYearTwo	78953000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Three LesseeOperatingLeaseLiabilityPaymentsDueYearThree	68871000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Four LesseeOperatingLeaseLiabilityPaymentsDueYearFour	59137000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Five LesseeOperatingLeaseLiabilityPaymentsDueYearFive	48738000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due After Year Five LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive	286035000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	632045000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	66796000	USD
CY2020	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	3133052000	USD
CY2019	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	2422788000	USD
CY2018	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	2132606000	USD
CY2020	us-gaap	Schedule Of Liability For Unpaid Claims And Claims Adjustment Expense ScheduleOfLiabilityForUnpaidClaimsAndClaimsAdjustmentExpense	The following table presents a reconciliation of consolidated beginning and ending reserves for losses and loss adjustment expenses.<table style="border-collapse:collapse;display:inline-table;vertical-align:top;width:100.000%"><tr><td style="width:1.0%"/><td style="width:57.454%"/><td style="width:0.1%"/><td style="width:1.0%"/><td style="width:12.321%"/><td style="width:0.1%"/><td style="width:0.1%"/><td style="width:0.389%"/><td style="width:0.1%"/><td style="width:1.0%"/><td style="width:12.321%"/><td style="width:0.1%"/><td style="width:0.1%"/><td style="width:0.389%"/><td style="width:0.1%"/><td style="width:1.0%"/><td style="width:12.326%"/><td style="width:0.1%"/></tr><tr><td colspan="3" style="padding:0 1pt"/><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:400;line-height:100%">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-style:italic;font-weight:400;line-height:100%;text-decoration:underline">(dollars in thousands)</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:400;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:400;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 for losses and loss adjustment expenses, beginning of 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:700;line-height:100%">$</span></td><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">9,475,261</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%"> </span></td><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">$</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%">9,214,443 </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%">8,964,945 </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 2px 19pt;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%">Effect of foreign currency rate changes on beginning of year balance</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:700;line-height:100%">68,368</span><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%">18,857 </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%">(69,119)</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 19pt;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%">Effect of adoption of ASC 326 (see note 1)</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:700;line-height:100%">3,849</span><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%">— </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%">Adjusted net reserves for losses and loss adjustment expenses, beginning of year</span></td><td colspan="2" style="background-color:#ffffff;border-top:1pt solid #000;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:700;line-height:100%">9,547,478</span><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;border-top:1pt solid #000;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 #000;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%">9,233,300 </span></td><td style="background-color:#ffffff;border-top:1pt solid #000;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 #000;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%">8,895,826 </span></td><td style="background-color:#ffffff;border-top:1pt solid #000;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%">Incurred losses and loss adjustment expenses:</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 19pt;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:700;line-height:100%">4,073,325</span><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%">3,426,441 </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%">3,371,699 </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 19pt;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:700;line-height:100%">(606,414)</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%">(535,307)</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%">(551,040)</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 19pt;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%">Total incurred losses and loss adjustment expenses</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:700;line-height:100%">3,466,911</span><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;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%">2,891,134 </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%">2,820,659 </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%">Payments:</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 2px 19pt;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:700;line-height:100%">749,887</span><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%">671,208 </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%">666,515 </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 19pt;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:700;line-height:100%">1,779,980</span><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%">1,979,032 </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%">1,835,027 </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 19pt;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%">Total payments</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:700;line-height:100%">2,529,867</span><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;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%">2,650,240 </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%">2,501,542 </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%">Effect of foreign currency rate changes on current year activity</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:700;line-height:100%">1,195</span><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 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%">1,067 </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%">(500)</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="display:none"/><td colspan="3" style="display:none"/><td colspan="3" style="display:none"/><td colspan="3" style="display:none"/><td colspan="3" style="display:none"/><td colspan="3" style="display:none"/></tr><tr><td colspan="3" style="display:none"/><td colspan="3" style="display:none"/><td colspan="3" style="display:none"/><td colspan="3" style="display:none"/><td colspan="3" style="display:none"/><td colspan="3" style="display:none"/></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 for losses and loss adjustment expenses, 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:700;line-height:100%">10,485,717</span><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;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%">9,475,261 </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%">9,214,443 </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%">Reinsurance recoverables on unpaid losses</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:700;line-height:100%">5,736,659</span><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 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%">5,253,415 </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%">5,062,036 </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%">Gross reserves for losses and loss adjustment expenses, end of year</span></td><td style="background-color:#ffffff;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:700;line-height:100%">$</span></td><td style="background-color:#ffffff;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:700;line-height:100%">16,222,376</span><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;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:#ffffff;padding:0 1pt"/><td style="background-color:#ffffff;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%">$</span></td><td style="background-color:#ffffff;border-bottom:3pt double #000000;border-top:1pt solid #000000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">14,728,676 </span></td><td style="background-color:#ffffff;border-bottom:3pt double #000000;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#ffffff;padding:0 1pt"/><td style="background-color:#ffffff;border-bottom:3pt double #000000;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">$</span></td><td style="background-color:#ffffff;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%">14,276,479 </span></td><td style="background-color:#ffffff;border-bottom:3pt double #000000;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr></table>
CY2019Q4	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Net LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	9475261000	USD
CY2018Q4	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Net LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	9214443000	USD
CY2017Q4	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Net LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	8964945000	USD
CY2020Q4	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Opening Balance Adjustments LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseOpeningBalanceAdjustments	68368000	USD
CY2019Q4	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Opening Balance Adjustments LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseOpeningBalanceAdjustments	18857000	USD
CY2018Q4	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Opening Balance Adjustments LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseOpeningBalanceAdjustments	-69119000	USD
CY2020Q4	mkl	Liability For Unpaid Claims And Claims Adjustment Expense Effect Of Adoption Of Asc326 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseEffectOfAdoptionOfASC326	3849000	USD
CY2019Q4	mkl	Liability For Unpaid Claims And Claims Adjustment Expense Effect Of Adoption Of Asc326 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseEffectOfAdoptionOfASC326	0	USD
CY2018Q4	mkl	Liability For Unpaid Claims And Claims Adjustment Expense Effect Of Adoption Of Asc326 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseEffectOfAdoptionOfASC326	0	USD
CY2020Q4	mkl	Adjusted Liability For Unpaid Claims And Claims Adjustment Expense Net AdjustedLiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	9547478000	USD
CY2019Q4	mkl	Adjusted Liability For Unpaid Claims And Claims Adjustment Expense Net AdjustedLiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	9233300000	USD
CY2018Q4	mkl	Adjusted Liability For Unpaid Claims And Claims Adjustment Expense Net AdjustedLiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	8895826000	USD
CY2020	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Current Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersCurrentYearClaimsAndClaimsAdjustmentExpense	4073325000	USD
CY2019	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Current Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersCurrentYearClaimsAndClaimsAdjustmentExpense	3426441000	USD
CY2018	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Current Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersCurrentYearClaimsAndClaimsAdjustmentExpense	3371699000	USD
CY2020	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Prior Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense	-606414000	USD
CY2019	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Prior Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense	-535307000	USD
CY2018	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Prior Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense	-551040000	USD
CY2020	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Incurred Claims1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaims1	3466911000	USD
CY2019	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Incurred Claims1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaims1	2891134000	USD
CY2018	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Incurred Claims1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaims1	2820659000	USD
CY2020	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Current Year1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidCurrentYear1	749887000	USD
CY2019	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Current Year1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidCurrentYear1	671208000	USD
CY2018	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Current Year1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidCurrentYear1	666515000	USD
CY2020	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Prior Years1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidPriorYears1	1779980000	USD
CY2019	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Prior Years1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidPriorYears1	1979032000	USD
CY2018	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Prior Years1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidPriorYears1	1835027000	USD
CY2020	us-gaap	Payments For Losses And Loss Adjustment Expense PaymentsForLossesAndLossAdjustmentExpense	2529867000	USD
CY2019	us-gaap	Payments For Losses And Loss Adjustment Expense PaymentsForLossesAndLossAdjustmentExpense	2650240000	USD
CY2018	us-gaap	Payments For Losses And Loss Adjustment Expense PaymentsForLossesAndLossAdjustmentExpense	2501542000	USD
CY2020	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Foreign Currency Translation Gain Loss LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseForeignCurrencyTranslationGainLoss	1195000	USD
CY2019	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Foreign Currency Translation Gain Loss LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseForeignCurrencyTranslationGainLoss	1067000	USD
CY2018	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Foreign Currency Translation Gain Loss LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseForeignCurrencyTranslationGainLoss	-500000	USD
CY2020Q4	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Net LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	10485717000	USD
CY2019Q4	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Net LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	9475261000	USD
CY2018Q4	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Net LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	9214443000	USD
CY2020Q4	us-gaap	Reinsurance Receivables Incurred But Not Reported Claims ReinsuranceReceivablesIncurredButNotReportedClaims	5736659000	USD
CY2019Q4	us-gaap	Reinsurance Receivables Incurred But Not Reported Claims ReinsuranceReceivablesIncurredButNotReportedClaims	5253415000	USD
CY2018Q4	us-gaap	Reinsurance Receivables Incurred But Not Reported Claims ReinsuranceReceivablesIncurredButNotReportedClaims	5062036000	USD
CY2020Q4	us-gaap	Liability For Claims And Claims Adjustment Expense LiabilityForClaimsAndClaimsAdjustmentExpense	16222376000	USD
CY2019Q4	us-gaap	Liability For Claims And Claims Adjustment Expense LiabilityForClaimsAndClaimsAdjustmentExpense	14728676000	USD
CY2018Q4	us-gaap	Liability For Claims And Claims Adjustment Expense LiabilityForClaimsAndClaimsAdjustmentExpense	14276479000	USD
CY2020Q4	mkl	Ibnr Reserves Percentage Of Total Unpaid Losses And Loss Adjustment Expenses IBNRReservesPercentageOfTotalUnpaidLossesAndLossAdjustmentExpenses	0.66
CY2019Q4	mkl	Ibnr Reserves Percentage Of Total Unpaid Losses And Loss Adjustment Expenses IBNRReservesPercentageOfTotalUnpaidLossesAndLossAdjustmentExpenses	0.65
CY2020	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Prior Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense	-606400000	USD
CY2019	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Prior Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense	-535300000	USD
CY2018	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Prior Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense	-551000000.0	USD
CY2020Q4	us-gaap	Shortduration Insurance Contracts Liability For Unpaid Claims And Allocated Claim Adjustment Expense Net ShortdurationInsuranceContractsLiabilityForUnpaidClaimsAndAllocatedClaimAdjustmentExpenseNet	10243212000	USD
CY2020Q4	us-gaap	Reinsurance Recoverable For Unpaid Claims And Claims Adjustments ReinsuranceRecoverableForUnpaidClaimsAndClaimsAdjustments	5736659000	USD
CY2020Q4	us-gaap	Shortduration Insurance Contracts Liability For Unpaid Claims And Claims Adjustment Expense Accumulated Unallocated Claim Adjustment Expense ShortdurationInsuranceContractsLiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseAccumulatedUnallocatedClaimAdjustmentExpense	299000000	USD
CY2020Q4	mkl	Unpaid Losses And Loss Adjustment Expenses Unamortized Fair Value Adjustment UnpaidLossesAndLossAdjustmentExpensesUnamortizedFairValueAdjustment	-56495000	USD
CY2020Q4	us-gaap	Shortduration Insurance Contracts Liability For Unpaid Claims And Claim Adjustment Expense Aggregate Reconciling Items ShortdurationInsuranceContractsLiabilityForUnpaidClaimsAndClaimAdjustmentExpenseAggregateReconcilingItems	242505000	USD
CY2020Q4	us-gaap	Liability For Claims And Claims Adjustment Expense LiabilityForClaimsAndClaimsAdjustmentExpense	16222376000	USD
CY2020	us-gaap	Direct Premiums Written DirectPremiumsWritten	7753781000	USD
CY2020	us-gaap	Assumed Premiums Written AssumedPremiumsWritten	1512884000	USD
CY2020	us-gaap	Ceded Premiums Written CededPremiumsWritten	3334427000	USD
CY2020	us-gaap	Premiums Written Net PremiumsWrittenNet	5932238000	USD
CY2020	us-gaap	Direct Premiums Earned DirectPremiumsEarned	7442776000	USD
CY2020	us-gaap	Assumed Premiums Earned AssumedPremiumsEarned	1469086000	USD
CY2020	us-gaap	Ceded Premiums Earned CededPremiumsEarned	3299657000	USD
CY2020	us-gaap	Premiums Earned Net PremiumsEarnedNet	5612205000	USD
CY2019	us-gaap	Direct Premiums Written DirectPremiumsWritten	7341388000	USD
CY2019	us-gaap	Assumed Premiums Written AssumedPremiumsWritten	1438583000	USD
CY2019	us-gaap	Ceded Premiums Written CededPremiumsWritten	3367900000	USD
CY2019	us-gaap	Premiums Written Net PremiumsWrittenNet	5412071000	USD
CY2019	us-gaap	Direct Premiums Earned DirectPremiumsEarned	6962507000	USD
CY2019	us-gaap	Assumed Premiums Earned AssumedPremiumsEarned	1368153000	USD
CY2019	us-gaap	Ceded Premiums Earned CededPremiumsEarned	3280867000	USD
CY2019	us-gaap	Premiums Earned Net PremiumsEarnedNet	5049793000	USD
CY2018	us-gaap	Direct Premiums Written DirectPremiumsWritten	6584804000	USD
CY2018	us-gaap	Assumed Premiums Written AssumedPremiumsWritten	1279665000	USD
CY2018	us-gaap	Ceded Premiums Written CededPremiumsWritten	3076891000	USD
CY2018	us-gaap	Premiums Written Net PremiumsWrittenNet	4787578000	USD
CY2018	us-gaap	Direct Premiums Earned DirectPremiumsEarned	6235218000	USD
CY2019	mkl	Premiums Percentage Ceded To Gross PremiumsPercentageCededToGross	0.39
CY2018	us-gaap	Assumed Premiums Earned AssumedPremiumsEarned	1319613000	USD
CY2018	us-gaap	Ceded Premiums Earned CededPremiumsEarned	2842771000	USD
CY2018	us-gaap	Premiums Earned Net PremiumsEarnedNet	4712060000	USD
CY2020	mkl	Premiums Percentage Ceded To Gross PremiumsPercentageCededToGross	0.37
CY2018	mkl	Premiums Percentage Ceded To Gross PremiumsPercentageCededToGross	0.38
CY2020	us-gaap	Premiums Percentage Assumed To Net PremiumsPercentageAssumedToNet	0.26
CY2019	us-gaap	Premiums Percentage Assumed To Net PremiumsPercentageAssumedToNet	0.27
CY2018	us-gaap	Premiums Percentage Assumed To Net PremiumsPercentageAssumedToNet	0.28
CY2020Q4	us-gaap	Liability For Future Policy Benefits Life LiabilityForFuturePolicyBenefitsLife	125856000	USD
CY2019Q4	us-gaap	Liability For Future Policy Benefits Life LiabilityForFuturePolicyBenefitsLife	125094000	USD
CY2020Q4	us-gaap	Liability For Future Policy Benefits Individual And Group Annuities And Supplementary Contracts LiabilityForFuturePolicyBenefitsIndividualAndGroupAnnuitiesAndSupplementaryContracts	900298000	USD
CY2019Q4	us-gaap	Liability For Future Policy Benefits Individual And Group Annuities And Supplementary Contracts LiabilityForFuturePolicyBenefitsIndividualAndGroupAnnuitiesAndSupplementaryContracts	813476000	USD
CY2020Q4	us-gaap	Liability For Future Policy Benefits Disability And Accident Benefits LiabilityForFuturePolicyBenefitsDisabilityAndAccidentBenefits	43832000	USD
CY2019Q4	us-gaap	Liability For Future Policy Benefits Disability And Accident Benefits LiabilityForFuturePolicyBenefitsDisabilityAndAccidentBenefits	47159000	USD
CY2020Q4	us-gaap	Liability For Future Policy Benefits LiabilityForFuturePolicyBenefits	1069986000	USD
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CY2020	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	7170000	USD
CY2019	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	16696000	USD
CY2018	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	8291000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	168682000	USD
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CY2020Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	24396000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	45544000	USD
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CY2019Q4	us-gaap	Deferred Tax Liabilities Deferred Expense Deferred Policy Acquisition Cost DeferredTaxLiabilitiesDeferredExpenseDeferredPolicyAcquisitionCost	113243000	USD
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CY2019Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	101426000	USD
CY2020Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	1652577000	USD
CY2019Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	1395368000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	986135000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	860720000	USD
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CY2020Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	50000000	shares
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CY2020Q2	us-gaap	Preferred Stock Redemption Price Per Share PreferredStockRedemptionPricePerShare	1000
CY2020	us-gaap	Dividends Preferred Stock DividendsPreferredStock	18400000	USD
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CY2020	us-gaap	Temporary Equity Accretion To Redemption Value Adjustment TemporaryEquityAccretionToRedemptionValueAdjustment	28705000	USD
CY2019	us-gaap	Temporary Equity Accretion To Redemption Value Adjustment TemporaryEquityAccretionToRedemptionValueAdjustment	-1105000	USD
CY2018	us-gaap	Temporary Equity Accretion To Redemption Value Adjustment TemporaryEquityAccretionToRedemptionValueAdjustment	4828000	USD
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CY2019	mkl	Adjusted Net Income Loss AdjustedNetIncomeLoss	1791571000	USD
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CY2020	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	13823000	shares
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	13881000	shares
CY2018	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	13923000	shares
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CY2018Q1	us-gaap	Revenues Revenues	1575471000	USD
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CY2018Q3	us-gaap	Revenues Revenues	2235949000	USD
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CY2018Q4	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	-751543000	USD
CY2018Q1	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	-174839000	USD
CY2018Q2	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	164336000	USD
CY2018Q3	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	315106000	USD
CY2018Q4	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	-680373000	USD
CY2018Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	-4.25
CY2018Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	20.01
CY2018Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	28.56
CY2018Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	-53.88
CY2018Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	-4.25
CY2018Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	19.97
CY2018Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	28.50
CY2018Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	-53.88

Files In Submission

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0001096343-21-000032.txt	Edgar Link	pending
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$MKL
MARKEL GROUP INC. Stock $mkl

2020 Q4 Form 10-K Financial Statement

#000109634321000032 Filed on February 19, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$MKL MARKEL GROUP INC. Stock $mkl

2020 Q4 Form 10-K Financial Statement

#000109634321000032 Filed on February 19, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$MKL
MARKEL GROUP INC. Stock $mkl