$GBCI
GLACIER BANCORP, INC. Stock $gbci

$gbci Overview Financials Valuation SEC Filings Company Website

2020 Q4 Form 10-K Financial Statement

#000086867121000037 Filed on March 01, 2021

Income Statement

Concept	2020 Q4	2019 Q4	2019 Q3
Revenue	$171.3M	$145.3M	$142.4M
YoY Change	17.91%	15.94%	15.86%
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	$7.900M	$7.500M	$7.000M
YoY Change	5.33%	19.05%	22.81%
% of Gross Profit
Operating Expenses
YoY Change
Operating Profit
YoY Change
Interest Expense	$5.550M	$8.833M	$10.95M
YoY Change	-37.17%	-6.39%	19.51%
% of Operating Profit
Other Income/Expense, Net
YoY Change
Pretax Income	$100.8M	$69.61M	$63.82M
YoY Change	44.81%	13.66%	6.13%
Income Tax	$18.95M	$12.20M	$12.21M
% Of Pretax Income	18.8%	17.53%	19.13%
Net Earnings	$81.86M	$57.41M	$51.61M
YoY Change	42.59%	15.75%	4.61%
Net Earnings / Revenue	47.79%	39.52%	36.24%
Basic Earnings Per Share	$0.86	$0.62	$0.57
Diluted Earnings Per Share	$0.86	$0.62	$0.57
COMMON SHARES
Basic Shares Outstanding	95.41M shares	92.19M shares	90.29M shares
Diluted Shares Outstanding			90.45M shares

Balance Sheet

Concept	2020 Q4	2019 Q4	2019 Q3
SHORT-TERM ASSETS
Cash & Short-Term Investments
YoY Change
Cash & Equivalents	$633.1M	$331.0M	$406.4M
Short-Term Investments
Other Short-Term Assets
YoY Change
Inventory
Prepaid Expenses
Receivables
Other Receivables
Total Short-Term Assets
YoY Change
LONG-TERM ASSETS
Property, Plant & Equipment	$272.8M	$263.2M	$307.6M
YoY Change	3.63%	8.99%	28.7%
Goodwill	$514.0M	$456.4M	$456.4M
YoY Change	12.62%	57.61%	57.64%
Intangibles
YoY Change
Long-Term Investments
YoY Change
Other Assets		$2.000M	$0.00
YoY Change		-91.67%	-100.0%
Total Long-Term Assets
YoY Change
TOTAL ASSETS
Total Short-Term Assets
Total Long-Term Assets
Total Assets	$18.50B	$13.68B	$13.72B
YoY Change	35.23%	12.95%	15.2%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable	$3.000M	$5.000M	$4.000M
YoY Change	-40.0%	25.0%	0.0%
Accrued Expenses	$50.00M	$44.00M	$44.00M
YoY Change	13.64%
Deferred Revenue
YoY Change
Short-Term Debt	$1.005B	$570.0M	$559.0M
YoY Change	76.32%	43.94%	36.67%
Long-Term Debt Due	$0.00	$0.00	$0.00
YoY Change
Total Short-Term Liabilities	$53.00M	$49.00M	$48.00M
YoY Change	8.16%	1125.0%	1100.0%
LONG-TERM LIABILITIES
Long-Term Debt	$173.0M	$169.0M	$155.0M
YoY Change	2.37%	13.42%	7.64%
Other Long-Term Liabilities	$145.0M	$121.0M	$126.0M
YoY Change	19.83%	3.42%	22.33%
Total Long-Term Liabilities	$318.0M	$290.0M	$281.0M
YoY Change	9.66%	9.02%	13.77%
TOTAL LIABILITIES
Total Short-Term Liabilities	$53.00M	$49.00M	$48.00M
Total Long-Term Liabilities	$318.0M	$290.0M	$281.0M
Total Liabilities	$16.20B	$11.72B	$11.77B
YoY Change	38.16%	10.6%	12.95%
SHAREHOLDERS EQUITY
Retained Earnings	$667.9M	$541.1M	$528.6M
YoY Change	23.45%	14.34%	12.22%
Common Stock	$1.495B	$1.379B	$1.376B
YoY Change	8.45%	31.13%	30.97%
Preferred Stock
YoY Change
Treasury Stock (at cost)
YoY Change
Treasury Stock Shares
Shareholders Equity	$2.307B	$1.961B	$1.953B
YoY Change
Total Liabilities & Shareholders Equity	$18.50B	$13.68B	$13.72B
YoY Change	35.23%	12.95%	15.2%

Cashflow Statement

Concept	2020 Q4	2019 Q4	2019 Q3
OPERATING ACTIVITIES
Net Income	$81.86M	$57.41M	$51.61M
YoY Change	42.59%	15.75%	4.61%
Depreciation, Depletion And Amortization	$7.900M	$7.500M	$7.000M
YoY Change	5.33%	19.05%	22.81%
Cash From Operating Activities	$75.70M	$112.2M	$28.70M
YoY Change	-32.53%	-0.88%	-57.98%
INVESTING ACTIVITIES
Capital Expenditures	-$3.600M	-$2.200M	-$2.300M
YoY Change	63.64%	-52.17%	-14.81%
Acquisitions
YoY Change
Other Investing Activities	-$681.3M	-$96.70M	$130.7M
YoY Change	604.55%	-71.31%	-246.52%
Cash From Investing Activities	-$684.9M	-$98.90M	$128.3M
YoY Change	592.52%	-71.06%	-239.61%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	472.3M	-88.80M	18.10M
YoY Change	-631.87%	-170.93%	-148.53%
NET CHANGE
Cash From Operating Activities	75.70M	112.2M	28.70M
Cash From Investing Activities	-684.9M	-98.90M	128.3M
Cash From Financing Activities	472.3M	-88.80M	18.10M
Net Change In Cash	-136.9M	-75.50M	175.1M
YoY Change	81.32%	-26.91%	-387.52%
FREE CASH FLOW
Cash From Operating Activities	$75.70M	$112.2M	$28.70M
Capital Expenditures	-$3.600M	-$2.200M	-$2.300M
Free Cash Flow	$79.30M	$114.4M	$31.00M
YoY Change	-30.68%	-2.89%	-56.34%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
CY2020	dei	Entity Central Index Key EntityCentralIndexKey	0000868671
CY2020	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2020
CY2020	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	FY
CY2020	dei	Amendment Flag AmendmentFlag	false
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CY2020	us-gaap	Accounting Standards Update Extensible List AccountingStandardsUpdateExtensibleList	us-gaap:AccountingStandardsUpdate201613Member
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CY2020	gbci	Number Of Years Before Allowed To Prepay Debt NumberOfYearsBeforeAllowedToPrepayDebt	5
CY2020	dei	Document Type DocumentType	10-K
CY2020	dei	Document Annual Report DocumentAnnualReport	true
CY2020	dei	Document Period End Date DocumentPeriodEndDate	2020-12-31
CY2020	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
CY2020	dei	Document Transition Report DocumentTransitionReport	false
CY2020	dei	Entity File Number EntityFileNumber	000-18911
CY2020	dei	Entity Registrant Name EntityRegistrantName	GLACIER BANCORP, INC.
CY2020	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	MT
CY2020	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	81-0519541
CY2020	dei	Entity Address Address Line1 EntityAddressAddressLine1	49 Commons Loop
CY2020	dei	Entity Address City Or Town EntityAddressCityOrTown	Kalispell,
CY2020	dei	Entity Address State Or Province EntityAddressStateOrProvince	MT
CY2020	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	59901
CY2020	dei	City Area Code CityAreaCode	(406)
CY2020	dei	Local Phone Number LocalPhoneNumber	756-4200
CY2020	dei	Security12b Title Security12bTitle	Common Stock, $0.01 par value
CY2020	dei	Trading Symbol TradingSymbol	GBCI
CY2020	dei	Security Exchange Name SecurityExchangeName	NASDAQ
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CY2019	us-gaap	Noninterest Income NoninterestIncome	130774000	USD
CY2018	us-gaap	Noninterest Income NoninterestIncome	118824000	USD
CY2020	us-gaap	Labor And Related Expense LaborAndRelatedExpense	253047000	USD
CY2019	us-gaap	Labor And Related Expense LaborAndRelatedExpense	222753000	USD
CY2018	us-gaap	Labor And Related Expense LaborAndRelatedExpense	195056000	USD
CY2020	us-gaap	Occupancy Net OccupancyNet	37673000	USD
CY2019	us-gaap	Occupancy Net OccupancyNet	34497000	USD
CY2018	us-gaap	Occupancy Net OccupancyNet	30734000	USD
CY2020	us-gaap	Advertising Expense AdvertisingExpense	10201000	USD
CY2019	us-gaap	Advertising Expense AdvertisingExpense	10621000	USD
CY2018	us-gaap	Advertising Expense AdvertisingExpense	9566000	USD
CY2020	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	21132000	USD
CY2019	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	17392000	USD
CY2018	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	15911000	USD
CY2020	us-gaap	Foreclosed Real Estate Expense ForeclosedRealEstateExpense	923000	USD
CY2019	us-gaap	Foreclosed Real Estate Expense ForeclosedRealEstateExpense	1105000	USD
CY2018	us-gaap	Foreclosed Real Estate Expense ForeclosedRealEstateExpense	3221000	USD
CY2020	gbci	General Insurance And Federal Deposit Insurance Corporation Premium Expense GeneralInsuranceAndFederalDepositInsuranceCorporationPremiumExpense	4656000	USD
CY2019	gbci	General Insurance And Federal Deposit Insurance Corporation Premium Expense GeneralInsuranceAndFederalDepositInsuranceCorporationPremiumExpense	3771000	USD
CY2018	gbci	General Insurance And Federal Deposit Insurance Corporation Premium Expense GeneralInsuranceAndFederalDepositInsuranceCorporationPremiumExpense	5075000	USD
CY2020	gbci	Loss On Hedging Activity LossOnHedgingActivity	0	USD
CY2019	gbci	Loss On Hedging Activity LossOnHedgingActivity	13528000	USD
CY2018	gbci	Loss On Hedging Activity LossOnHedgingActivity	0	USD
CY2020	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	10370000	USD
CY2019	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	8485000	USD
CY2018	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	6270000	USD
CY2020	us-gaap	Other Noninterest Expense OtherNoninterestExpense	66809000	USD
CY2019	us-gaap	Other Noninterest Expense OtherNoninterestExpense	62775000	USD
CY2018	us-gaap	Other Noninterest Expense OtherNoninterestExpense	54294000	USD
CY2020	us-gaap	Noninterest Expense NoninterestExpense	404811000	USD
CY2019	us-gaap	Noninterest Expense NoninterestExpense	374927000	USD
CY2018	us-gaap	Noninterest Expense NoninterestExpense	320127000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	328040000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	259194000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	222209000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	61640000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	48650000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	40331000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	266400000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	210544000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	181878000	USD
CY2020	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.81
CY2020	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.33
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.39
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.18
CY2020	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.81
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.38
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.17
CY2019	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.31
CY2018	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.31
CY2020	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	94883864	shares
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	88255290	shares
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	83603515	shares
CY2020	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	94932353	shares
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	88385775	shares
CY2018	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	83677185	shares
CY2020	us-gaap	Net Income Loss NetIncomeLoss	266400000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	210544000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	181878000	USD
CY2020	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	139208000	USD
CY2019	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	77158000	USD
CY2018	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	-15608000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	1138000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	14423000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	-12000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Before Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax	138070000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Before Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax	62735000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Before Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax	-15596000	USD
CY2020	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	34853000	USD
CY2019	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	15896000	USD
CY2018	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	-3952000	USD
CY2020	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	103217000	USD
CY2019	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	46839000	USD
CY2018	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	-11644000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax	-472000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax	-7047000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax	3286000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Before Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax	0	USD
CY2019	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Before Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax	-10816000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Before Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax	-2334000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification Before Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationBeforeTax	-472000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification Before Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationBeforeTax	3769000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification Before Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationBeforeTax	5620000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTax	-119000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTax	955000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTax	1424000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	-353000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	2814000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	4196000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	102864000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	49653000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-7448000	USD
CY2020	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	369264000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	260197000	USD
CY2018	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	174430000	USD
CY2017Q4	us-gaap	Stockholders Equity StockholdersEquity	1199057000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	181878000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-7448000	USD
CY2018	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.31
CY2018	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	110954000	USD
CY2018	us-gaap	Stock Issued During Period Value Acquisitions StockIssuedDuringPeriodValueAcquisitions	250807000	USD
CY2018	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	0	USD
CY2018	us-gaap	Adjustments To Additional Paid In Capital Share Based Compensation Restricted Stock Units Requisite Service Period Recognition AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationRestrictedStockUnitsRequisiteServicePeriodRecognition	2514000	USD
CY2018Q4	us-gaap	Stockholders Equity StockholdersEquity	1515854000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	210544000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	49653000	USD
CY2019	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.31
CY2019	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	117563000	USD
CY2019	us-gaap	Stock Issued During Period Value Acquisitions StockIssuedDuringPeriodValueAcquisitions	316538000	USD
CY2019	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	0	USD
CY2019	us-gaap	Adjustments To Additional Paid In Capital Share Based Compensation Restricted Stock Units Requisite Service Period Recognition AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationRestrictedStockUnitsRequisiteServicePeriodRecognition	10821000	USD
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	1960733000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	266400000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	102864000	USD
CY2020	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.33
CY2020	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	127159000	USD
CY2020	us-gaap	Stock Issued During Period Value Acquisitions StockIssuedDuringPeriodValueAcquisitions	112133000	USD
CY2020	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	0	USD
CY2020	us-gaap	Adjustments To Additional Paid In Capital Share Based Compensation Restricted Stock Units Requisite Service Period Recognition AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationRestrictedStockUnitsRequisiteServicePeriodRecognition	4417000	USD
CY2020Q4	us-gaap	Stockholders Equity StockholdersEquity	2307041000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	266400000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	210544000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	181878000	USD
CY2020	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	39765000	USD
CY2019	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	57000	USD
CY2018	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	9953000	USD
CY2020	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-16893000	USD
CY2019	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-12985000	USD
CY2018	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-13095000	USD
CY2020	gbci	Accretion Amortization Of Discounts And Premiums Business Combinations AccretionAmortizationOfDiscountsAndPremiumsBusinessCombinations	57627000	USD
CY2019	gbci	Accretion Amortization Of Discounts And Premiums Business Combinations AccretionAmortizationOfDiscountsAndPremiumsBusinessCombinations	3712000	USD
CY2018	gbci	Accretion Amortization Of Discounts And Premiums Business Combinations AccretionAmortizationOfDiscountsAndPremiumsBusinessCombinations	3963000	USD
CY2020	us-gaap	Amortization Of Financing Costs AmortizationOfFinancingCosts	0	USD
CY2019	us-gaap	Amortization Of Financing Costs AmortizationOfFinancingCosts	4630000	USD
CY2018	us-gaap	Amortization Of Financing Costs AmortizationOfFinancingCosts	1649000	USD
CY2020	us-gaap	Payments For Origination And Purchases Of Loans Held For Sale PaymentsForOriginationAndPurchasesOfLoansHeldForSale	2070843000	USD
CY2019	us-gaap	Payments For Origination And Purchases Of Loans Held For Sale PaymentsForOriginationAndPurchasesOfLoansHeldForSale	983988000	USD
CY2018	us-gaap	Payments For Origination And Purchases Of Loans Held For Sale PaymentsForOriginationAndPurchasesOfLoansHeldForSale	841451000	USD
CY2020	us-gaap	Proceeds From Sale Of Mortgage Loans Held For Sale ProceedsFromSaleOfMortgageLoansHeldForSale	2093549000	USD
CY2019	us-gaap	Proceeds From Sale Of Mortgage Loans Held For Sale ProceedsFromSaleOfMortgageLoansHeldForSale	985345000	USD
CY2018	us-gaap	Proceeds From Sale Of Mortgage Loans Held For Sale ProceedsFromSaleOfMortgageLoansHeldForSale	896145000	USD
CY2020	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	99450000	USD
CY2019	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	34064000	USD
CY2018	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	27134000	USD
CY2020	us-gaap	Gain Loss On Sale Of Investments GainLossOnSaleOfInvestments	1139000	USD
CY2019	us-gaap	Gain Loss On Sale Of Investments GainLossOnSaleOfInvestments	14415000	USD
CY2019	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	8485000	USD
CY2018	us-gaap	Gain Loss On Sale Of Investments GainLossOnSaleOfInvestments	-1113000	USD
CY2020	us-gaap	Life Insurance Corporate Or Bank Owned Change In Value LifeInsuranceCorporateOrBankOwnedChangeInValue	2724000	USD
CY2019	us-gaap	Life Insurance Corporate Or Bank Owned Change In Value LifeInsuranceCorporateOrBankOwnedChangeInValue	2245000	USD
CY2018	us-gaap	Life Insurance Corporate Or Bank Owned Change In Value LifeInsuranceCorporateOrBankOwnedChangeInValue	2234000	USD
CY2020	us-gaap	Share Based Compensation ShareBasedCompensation	3629000	USD
CY2019	us-gaap	Share Based Compensation ShareBasedCompensation	7475000	USD
CY2018	us-gaap	Share Based Compensation ShareBasedCompensation	3122000	USD
CY2020	us-gaap	Depreciation Nonproduction DepreciationNonproduction	20420000	USD
CY2019	us-gaap	Depreciation Nonproduction DepreciationNonproduction	18592000	USD
CY2018	us-gaap	Depreciation Nonproduction DepreciationNonproduction	16019000	USD
CY2020	us-gaap	Gains Losses On Sales Of Other Real Estate GainsLossesOnSalesOfOtherRealEstate	-139000	USD
CY2019	us-gaap	Gains Losses On Sales Of Other Real Estate GainsLossesOnSalesOfOtherRealEstate	-73000	USD
CY2018	us-gaap	Gains Losses On Sales Of Other Real Estate GainsLossesOnSalesOfOtherRealEstate	-2130000	USD
CY2020	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-6863000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-356000	USD
CY2018	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	6861000	USD
CY2020	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	10370000	USD
CY2018	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	6270000	USD
CY2020	gbci	Variable Interest Entities Investment Amortization VariableInterestEntitiesInvestmentAmortization	11282000	USD
CY2019	gbci	Variable Interest Entities Investment Amortization VariableInterestEntitiesInvestmentAmortization	9700000	USD
CY2018	gbci	Variable Interest Entities Investment Amortization VariableInterestEntitiesInvestmentAmortization	7639000	USD
CY2020	us-gaap	Increase Decrease In Accrued Interest Receivable Net IncreaseDecreaseInAccruedInterestReceivableNet	17663000	USD
CY2019	us-gaap	Increase Decrease In Accrued Interest Receivable Net IncreaseDecreaseInAccruedInterestReceivableNet	-1899000	USD
CY2018	us-gaap	Increase Decrease In Accrued Interest Receivable Net IncreaseDecreaseInAccruedInterestReceivableNet	2741000	USD
CY2020	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	20926000	USD
CY2019	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	-5078000	USD
CY2018	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	-348000	USD
CY2020	us-gaap	Increase Decrease In Interest Payable Net IncreaseDecreaseInInterestPayableNet	-1507000	USD
CY2019	us-gaap	Increase Decrease In Interest Payable Net IncreaseDecreaseInInterestPayableNet	312000	USD
CY2018	us-gaap	Increase Decrease In Interest Payable Net IncreaseDecreaseInInterestPayableNet	357000	USD
CY2020	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	5840000	USD
CY2019	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	254000	USD
CY2018	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	11655000	USD
CY2020	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	189545000	USD
CY2019	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	226649000	USD
CY2018	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	280711000	USD
CY2020	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	0	USD
CY2019	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	712113000	USD
CY2018	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	226842000	USD
CY2020	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	758879000	USD
CY2019	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	711838000	USD
CY2018	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	357876000	USD
CY2020	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	3254912000	USD
CY2019	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	1224231000	USD
CY2018	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	820333000	USD
CY2020	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	32735000	USD
CY2019	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	58750000	USD
CY2018	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	76832000	USD
CY2020	us-gaap	Proceeds From Loan And Lease Originations And Principal Collections1 ProceedsFromLoanAndLeaseOriginationsAndPrincipalCollections1	4732941000	USD
CY2019	us-gaap	Proceeds From Loan And Lease Originations And Principal Collections1 ProceedsFromLoanAndLeaseOriginationsAndPrincipalCollections1	3250220000	USD
CY2018	us-gaap	Proceeds From Loan And Lease Originations And Principal Collections1 ProceedsFromLoanAndLeaseOriginationsAndPrincipalCollections1	2691953000	USD
CY2020	gbci	Payments For Loans Originated Or Acquired PaymentsForLoansOriginatedOrAcquired	5864038000	USD
CY2019	gbci	Payments For Loans Originated Or Acquired PaymentsForLoansOriginatedOrAcquired	3623548000	USD
CY2018	gbci	Payments For Loans Originated Or Acquired PaymentsForLoansOriginatedOrAcquired	3460227000	USD
CY2020	us-gaap	Payments For Proceeds From Productive Assets PaymentsForProceedsFromProductiveAssets	11717000	USD
CY2019	us-gaap	Payments For Proceeds From Productive Assets PaymentsForProceedsFromProductiveAssets	16398000	USD
CY2018	us-gaap	Payments For Proceeds From Productive Assets PaymentsForProceedsFromProductiveAssets	18637000	USD
CY2020	us-gaap	Proceeds From Sale Of Wholly Owned Real Estate And Real Estate Acquired In Settlement Of Loans ProceedsFromSaleOfWhollyOwnedRealEstateAndRealEstateAcquiredInSettlementOfLoans	5572000	USD
CY2019	us-gaap	Proceeds From Sale Of Wholly Owned Real Estate And Real Estate Acquired In Settlement Of Loans ProceedsFromSaleOfWhollyOwnedRealEstateAndRealEstateAcquiredInSettlementOfLoans	4670000	USD
CY2018	us-gaap	Proceeds From Sale Of Wholly Owned Real Estate And Real Estate Acquired In Settlement Of Loans ProceedsFromSaleOfWhollyOwnedRealEstateAndRealEstateAcquiredInSettlementOfLoans	9385000	USD
CY2020	us-gaap	Proceeds From Sale Of Federal Home Loan Bank Stock ProceedsFromSaleOfFederalHomeLoanBankStock	76618000	USD
CY2019	us-gaap	Proceeds From Sale Of Federal Home Loan Bank Stock ProceedsFromSaleOfFederalHomeLoanBankStock	118516000	USD
CY2018	us-gaap	Proceeds From Sale Of Federal Home Loan Bank Stock ProceedsFromSaleOfFederalHomeLoanBankStock	87221000	USD
CY2020	us-gaap	Payments To Acquire Federal Home Loan Bank Stock PaymentsToAcquireFederalHomeLoanBankStock	71399000	USD
CY2019	us-gaap	Payments To Acquire Federal Home Loan Bank Stock PaymentsToAcquireFederalHomeLoanBankStock	97597000	USD
CY2018	us-gaap	Payments To Acquire Federal Home Loan Bank Stock PaymentsToAcquireFederalHomeLoanBankStock	87975000	USD
CY2020	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	0	USD
CY2019	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	0	USD
CY2018	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	1331000	USD
CY2020	us-gaap	Payments To Acquire Other Investments PaymentsToAcquireOtherInvestments	12088000	USD
CY2019	us-gaap	Payments To Acquire Other Investments PaymentsToAcquireOtherInvestments	16348000	USD
CY2018	us-gaap	Payments To Acquire Other Investments PaymentsToAcquireOtherInvestments	37956000	USD
CY2020	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	-43713000	USD
CY2019	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	-79333000	USD
CY2018	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	-101268000	USD
CY2020	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-3563696000	USD
CY2019	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-42682000	USD
CY2018	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-872420000	USD
CY2020	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	3418199000	USD
CY2019	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	285856000	USD
CY2018	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	599037000	USD
CY2020	us-gaap	Proceeds From Payments For In Securities Sold Under Agreements To Repurchase ProceedsFromPaymentsForInSecuritiesSoldUnderAgreementsToRepurchase	427510000	USD
CY2019	us-gaap	Proceeds From Payments For In Securities Sold Under Agreements To Repurchase ProceedsFromPaymentsForInSecuritiesSoldUnderAgreementsToRepurchase	172264000	USD
CY2018	us-gaap	Proceeds From Payments For In Securities Sold Under Agreements To Repurchase ProceedsFromPaymentsForInSecuritiesSoldUnderAgreementsToRepurchase	4398000	USD
CY2020	us-gaap	Proceeds From Repayments Of Short Term Debt Maturing In Three Months Or Less ProceedsFromRepaymentsOfShortTermDebtMaturingInThreeMonthsOrLess	-30000000	USD
CY2019	us-gaap	Proceeds From Repayments Of Short Term Debt Maturing In Three Months Or Less ProceedsFromRepaymentsOfShortTermDebtMaturingInThreeMonthsOrLess	-255000000	USD
CY2018	us-gaap	Proceeds From Repayments Of Short Term Debt Maturing In Three Months Or Less ProceedsFromRepaymentsOfShortTermDebtMaturingInThreeMonthsOrLess	85000000	USD
CY2020	us-gaap	Proceeds From Federal Home Loan Bank Borrowings ProceedsFromFederalHomeLoanBankBorrowings	30000000	USD
CY2019	us-gaap	Proceeds From Federal Home Loan Bank Borrowings ProceedsFromFederalHomeLoanBankBorrowings	0	USD
CY2018	us-gaap	Proceeds From Federal Home Loan Bank Borrowings ProceedsFromFederalHomeLoanBankBorrowings	0	USD
CY2020	us-gaap	Repayments Of Federal Home Loan Bank Borrowings RepaymentsOfFederalHomeLoanBankBorrowings	38589000	USD
CY2019	us-gaap	Repayments Of Federal Home Loan Bank Borrowings RepaymentsOfFederalHomeLoanBankBorrowings	151160000	USD
CY2018	us-gaap	Repayments Of Federal Home Loan Bank Borrowings RepaymentsOfFederalHomeLoanBankBorrowings	1198000	USD
CY2020	us-gaap	Proceeds From Repayments Of Other Debt ProceedsFromRepaymentsOfOtherDebt	564000	USD
CY2019	us-gaap	Proceeds From Repayments Of Other Debt ProceedsFromRepaymentsOfOtherDebt	14109000	USD
CY2018	us-gaap	Proceeds From Repayments Of Other Debt ProceedsFromRepaymentsOfOtherDebt	-5059000	USD
CY2020	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	131263000	USD
CY2019	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	124468000	USD
CY2018	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	85493000	USD
CY2020	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	1082000	USD
CY2019	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	1293000	USD
CY2018	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	1214000	USD
CY2020	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	993000	USD
CY2019	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	2896000	USD
CY2018	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	24000	USD
CY2020	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	3676332000	USD
CY2019	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-56796000	USD
CY2018	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	595495000	USD
CY2020	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Excluding Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect	302181000	USD
CY2019	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Excluding Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect	127171000	USD
CY2018	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Excluding Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect	3786000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	330961000	USD
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	203790000	USD
CY2017Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	200004000	USD
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	633142000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	330961000	USD
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	203790000	USD
CY2020	us-gaap	Interest Paid Net InterestPaidNet	28822000	USD
CY2019	us-gaap	Interest Paid Net InterestPaidNet	42461000	USD
CY2018	us-gaap	Interest Paid Net InterestPaidNet	35174000	USD
CY2020	us-gaap	Income Taxes Paid IncomeTaxesPaid	63021000	USD
CY2019	us-gaap	Income Taxes Paid IncomeTaxesPaid	36817000	USD
CY2018	us-gaap	Income Taxes Paid IncomeTaxesPaid	26489000	USD
CY2020	us-gaap	Transfer Of Investments TransferOfInvestments	0	USD
CY2019	us-gaap	Transfer Of Investments TransferOfInvestments	0	USD
CY2018	us-gaap	Transfer Of Investments TransferOfInvestments	270331000	USD
CY2020	us-gaap	Transfer Of Other Real Estate TransferOfOtherRealEstate	215000	USD
CY2019	us-gaap	Transfer Of Other Real Estate TransferOfOtherRealEstate	7000	USD
CY2018	us-gaap	Transfer Of Other Real Estate TransferOfOtherRealEstate	406000	USD
CY2020	us-gaap	Transfer To Other Real Estate TransferToOtherRealEstate	2076000	USD
CY2019	us-gaap	Transfer To Other Real Estate TransferToOtherRealEstate	2349000	USD
CY2018	us-gaap	Transfer To Other Real Estate TransferToOtherRealEstate	4924000	USD
CY2020	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	7406000	USD
CY2019	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	9948000	USD
CY2018	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	0	USD
CY2020	gbci	Dividends Declared But Not Paid During The Period DividendsDeclaredButNotPaidDuringThePeriod	14572000	USD
CY2019	gbci	Dividends Declared But Not Paid During The Period DividendsDeclaredButNotPaidDuringThePeriod	18686000	USD
CY2018	gbci	Dividends Declared But Not Paid During The Period DividendsDeclaredButNotPaidDuringThePeriod	25726000	USD
CY2020	us-gaap	Stock Issued1 StockIssued1	112133000	USD
CY2019	us-gaap	Stock Issued1 StockIssued1	316538000	USD
CY2018	us-gaap	Stock Issued1 StockIssued1	250807000	USD
CY2020	gbci	Cash Consideration For Outstanding Shares CashConsiderationForOutstandingShares	13721000	USD
CY2019	gbci	Cash Consideration For Outstanding Shares CashConsiderationForOutstandingShares	16424000	USD
CY2018	gbci	Cash Consideration For Outstanding Shares CashConsiderationForOutstandingShares	16265000	USD
CY2020	gbci	Business Combination Effective Settlement Of A Pre Existing Relationship BusinessCombinationEffectiveSettlementOfAPreExistingRelationship	0	USD
CY2019	gbci	Business Combination Effective Settlement Of A Pre Existing Relationship BusinessCombinationEffectiveSettlementOfAPreExistingRelationship	0	USD
CY2018	gbci	Business Combination Effective Settlement Of A Pre Existing Relationship BusinessCombinationEffectiveSettlementOfAPreExistingRelationship	10054000	USD
CY2020	us-gaap	Noncash Or Part Noncash Acquisition Value Of Assets Acquired1 NoncashOrPartNoncashAcquisitionValueOfAssetsAcquired1	745420000	USD
CY2019	us-gaap	Noncash Or Part Noncash Acquisition Value Of Assets Acquired1 NoncashOrPartNoncashAcquisitionValueOfAssetsAcquired1	1357099000	USD
CY2018	us-gaap	Noncash Or Part Noncash Acquisition Value Of Assets Acquired1 NoncashOrPartNoncashAcquisitionValueOfAssetsAcquired1	1660882000	USD
CY2020	us-gaap	Noncash Or Part Noncash Acquisition Value Of Liabilities Assumed1 NoncashOrPartNoncashAcquisitionValueOfLiabilitiesAssumed1	619566000	USD
CY2019	us-gaap	Noncash Or Part Noncash Acquisition Value Of Liabilities Assumed1 NoncashOrPartNoncashAcquisitionValueOfLiabilitiesAssumed1	1024137000	USD
CY2018	us-gaap	Noncash Or Part Noncash Acquisition Value Of Liabilities Assumed1 NoncashOrPartNoncashAcquisitionValueOfLiabilitiesAssumed1	1383756000	USD
CY2020Q4	gbci	Number Of Bank Divisions NumberOfBankDivisions	16	division
CY2020	gbci	Maximum Period Of Original Maturity To Be Included In Cash And Cash Equivalents MaximumPeriodOfOriginalMaturityToBeIncludedInCashAndCashEquivalents	three months
CY2020Q4	gbci	Federal Reserve Balance Or Cash On Hand Required FederalReserveBalanceOrCashOnHandRequired	0	USD
CY2020	gbci	Minimum Period Past Due To Consider Loans As Delinquent MinimumPeriodPastDueToConsiderLoansAsDelinquent	P30D
CY2020	gbci	Minimum Period Past Due To Consider Loans As Non Accrual MinimumPeriodPastDueToConsiderLoansAsNonAccrual	P90D
CY2020	us-gaap	Financing Receivable Allowance For Credit Losses Policy For Uncollectible Amounts FinancingReceivableAllowanceForCreditLossesPolicyForUncollectibleAmounts	<div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%;text-decoration:underline">Allowance for Credit Losses - Loans Receivable</span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">The allowance for credit losses for loans receivable represents management’s estimate of credit losses over the expected contractual life of the loan portfolio. The estimate is determined based on the amortized cost of the loan portfolio including the loan balance adjusted for charge-offs, recoveries, deferred fees and costs, and loan discount and premiums. Recoveries are included only to the extent that such amounts were previously charged-off. The Company has elected to exclude accrued interest from the estimate of credit losses for loans. Determining the adequacy of the allowance is complex and requires a high degree of judgment by management about the effect of matters that are inherently uncertain. Subsequent evaluations of the then-existing loan portfolio, in light of the factors then prevailing, may result in significant changes in the allowance in future periods.</span></div><div style="text-align:justify"><span><br/></span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">The allowance is increased for estimated credit losses which are recorded as expense. The portion of loans and overdraft balances determined by management to be uncollectable are charged-off as a reduction to the allowance and recoveries of amounts previously charged-off increase the allowance. The Company’s charge-off policy is consistent with bank regulatory standards. Consumer loans generally are charged-off when the loan becomes over 120 days delinquent. Real estate acquired as a result of foreclosure or by deed-in-lieu of foreclosure is classified as other real estate owned (“OREO”) until such time as it is sold. </span></div><div><span><br/></span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">The expected credit loss estimate process involves procedures to consider the unique characteristics of each of the Company’s loan portfolio segments, which consist of residential real estate, commercial real estate, other commercial, home equity, and other consumer loans. When computing the allowance levels, credit loss assumptions are estimated using a model that categorizes loan pools based on loss history, credit and risk characteristics, including current conditions and reasonable and supportable forecasts about the future. The Company has determined a four consecutive quarter forecasting period is a reasonable and supportable period. Expected credit loss for periods beyond reasonable and supportable forecast periods are determined based on a reversion method which reverts back to historical loss estimate over a four consecutive quarter period on a straight-line basis.</span></div><div style="text-align:justify"><span><br/></span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">Credit quality is assessed and monitored by evaluating various attributes and the results of those evaluations are utilized in underwriting new loans and the process for estimating the expected credit losses. The following paragraphs describe the risk characteristics relevant to each portfolio segment.</span></div><div style="text-align:justify"><span><br/></span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-style:italic;font-weight:400;line-height:120%">Residential Real Estate.</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%"> Residential real estate loans are secured by owner-occupied 1-4 family residences. Repayment of these loans is primarily dependent on the personal income and credit rating of the borrowers. Credit risk in these loans is impacted by economic conditions within the Company’s market areas that affect the value of the residential property securing the loans and affect the borrowers' personal incomes. Mitigating risk factors for this loan segment include a large number of borrowers, geographic dispersion of market areas and the loans are originated for relatively smaller amounts.</span></div><div style="text-align:justify"><span><br/></span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-style:italic;font-weight:400;line-height:120%">Commercial Real Estate</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">. Commercial real estate loans typically involve larger principal amounts, and repayment of these loans is generally dependent on the successful operation of the property securing the loan and/or the business conducted on the property securing the loan. Credit risk in these loans is impacted by the creditworthiness of a borrower, valuation of the property securing the loan and conditions within the local economies in the Company’s diverse, geographic market areas.</span></div><div style="text-align:justify"><span><br/></span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-style:italic;font-weight:400;line-height:120%">Commercial</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">. Commercial loans consist of loans to commercial customers for use in financing working capital needs, equipment purchases and business expansions. The loans in this category are repaid primarily from the cash flow of a borrower’s principal business operation. Credit risk in these loans is driven by creditworthiness of a borrower and the economic conditions that impact the cash flow stability from business operations across the Company’s diverse, geographic market areas.</span></div><div style="text-align:justify"><span><br/></span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-style:italic;font-weight:400;line-height:120%">Home Equity</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">. Home equity loans consist of junior lien mortgages and first and junior lien lines of credit (revolving open-end and amortizing closed-end) secured by owner-occupied 1-4 family residences. Repayment of these loans is primarily dependent on the personal income and credit rating of the borrowers. Credit risk in these loans is impacted by economic conditions within the Company’s market areas that affect the value of the residential property securing the loans and affect the borrowers' personal incomes. Mitigating risk factors for this loan segment are a large number of borrowers, geographic dispersion of market areas and the loans are originated for terms that range from 10 to 15 years.</span></div><div style="text-align:justify"><span><br/></span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-style:italic;font-weight:400;line-height:120%">Other Consumer</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">. The other consumer loan portfolio consists of various short-term loans such as automobile loans and loans for other personal purposes. Repayment of these loans is primarily dependent on the personal income of the borrowers. Credit risk is driven by consumer economic factors (such as unemployment and general economic conditions in the Company’s diverse, geographic market area) and the creditworthiness of a borrower.</span></div><div style="text-align:justify"><span><br/></span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">The allowance is impacted by loan volumes, delinquency status, credit ratings, historical loss experiences, estimated prepayment speeds, weighted average lives and other conditions influencing loss expectations, such as reasonable and supportable forecasts of economic conditions. The methodology for estimating the amount of expected credit losses reported in the allowance has two basic components: 1) individual loans that do not share similar risk characteristics with other loans and the measurement of expected credit losses for such individual loans; and 2) the expected credit losses for pools of loans that share similar risk characteristics.</span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-style:italic;font-weight:400;line-height:120%">Loans that do not Share Similar Risk Characteristics with Other Loans. </span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">For a loan that does not share similar risk characteristics with other loans, expected credit loss is measured based on the net realizable value, that is, the difference between the discounted value of the expected future cash flows, based on the original effective interest rate, and the amortized cost basis of the loan. For these loans, the expected credit loss is equal to the amount by which the net realizable value of the loan is less than the amortized cost basis of the loan (which is net of previous charge-offs and deferred loan fees and costs), except when the loan is collateral-dependent, that is, when foreclosure is probable or the borrower is experiencing financial difficulty and repayment is expected to be provided substantially through the operation or sale of the collateral. In these cases, expected credit loss is measured as the difference between the amortized cost basis of the loan and the fair value of the collateral. The fair value of the collateral is adjusted for the estimated cost to sell if repayment or satisfaction of a loan is dependent on the sale (rather than only on the operation) of the collateral. The Company has determined that non-accrual loans do not share similar risk characteristics with other loans and these loans are individually evaluated for estimated allowance for credit losses. The Company, through its credit monitoring process, may also identify other loans that do no share similar risk characteristics and individually evaluate such loans. The starting point for determining the fair value of collateral is to obtain external appraisals or evaluations (new or updated). The valuation techniques used in preparing appraisals or evaluations (new or updated) include the cost approach, income approach, sales comparison approach, or a combination of the preceding valuation techniques. The Company’s credit department reviews appraisals, giving consideration to the highest and best use of the collateral. The appraisals or evaluations (new or updated) are reviewed at least quarterly and more frequently based on current market conditions, including deterioration in a borrower’s financial condition and when property values may be subject to significant volatility. Adjustments may be made to the fair value of the collateral after review and acceptance of the collateral appraisal or evaluation (new or updated).</span></div><div style="text-align:justify"><span><br/></span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-style:italic;font-weight:400;line-height:120%">Loans that Share Similar Risk Characteristics with other Loans. </span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">For estimating the allowance for loans that share similar risk characteristics with other loans, such loans are segregated into loan segments. Loans are designated into loan segments based on loans pooled by product types and similar risk characteristics or areas of risk concentration. In determining the ACL, the Company derives an estimated credit loss assumption from a model that categorizes loan pools based on loan type which is further segregated by the credit quality indicators. This model calculates an expected loss percentage for each loan segment by considering the non-discounted simple annual average historical loss rate of each loan segment (calculated through an “open pool” method), multiplying the loss rate by the amortized loan balance and incorporating that segment’s internally generated prepayment speed assumption and contractually scheduled remaining principal pay downs on a loan level basis. The annual historical loss rates are adjusted over a reasonable economic forecast period by a multiplier that is calculated based upon current national economic forecasts as a proportion of each segment’s historical average loss levels. The Company will then revert from the economic forecast period back to the historical average loss rate in a straight-line basis. After the reversion period, the loans will be assumed to experience their historical loss rate for the remainder of their contractual lives. The model applies the expected loss rate over the projected cash flows at the individual loan level and then aggregates the losses by loan segment in determining their quantitative allowance. The Company will also include qualitative adjustments to adjust the ACL on loan segments </span><span style="background-color:#ffffff;color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">to the extent the current or future market conditions are believed to vary substantially from historical conditions in regards to:</span></div><div style="margin-top:6pt;padding-left:36pt;text-align:justify;text-indent:-18pt"><span style="background-color:#ffffff;color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="background-color:#ffffff;color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:14.5pt">lending policies and procedures;</span></div><div style="padding-left:36pt;text-align:justify;text-indent:-18pt"><span style="background-color:#ffffff;color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="background-color:#ffffff;color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:14.5pt">i</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">nternational, national, regional and local economic business conditions and developments that affect the collectability of the portfolio, including the condition of various markets;</span></div><div style="padding-left:36pt;text-align:justify;text-indent:-18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:14.5pt">the nature and volume of the loan portfolio including the terms of the loans;</span></div><div style="padding-left:36pt;text-align:justify;text-indent:-18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:14.5pt">the experience, ability, and depth of the lending management and other relevant staff;</span></div><div style="padding-left:36pt;text-align:justify;text-indent:-18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:14.5pt">the volume and severity of past due and adversely classified or graded loans and the volume of non-accrual loans;</span></div><div style="padding-left:36pt;text-align:justify;text-indent:-18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:14.5pt">the quality of our loan review system;</span></div><div style="padding-left:36pt;text-align:justify;text-indent:-18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:14.5pt">the value of underlying collateral for collateralized loans;</span></div><div style="padding-left:36pt;text-align:justify;text-indent:-18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:14.5pt">the existence and effect of any concentrations of credit, and changes in the level of concentrations; and</span></div><div style="padding-left:36pt;text-align:justify;text-indent:-18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:14.5pt">the effect of external factors such as competition and legal and regulatory requirements on the level of estimated credit losses in the existing portfolio. </span></div><div><span><br/></span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">The Company regularly reviews loans in the portfolio to assess credit quality indicators and to determine the appropriate loan classification and grading in accordance with applicable bank regulations. The primary credit quality indicator for residential, home equity and other consumer loans is the days past due status, which consists of the following categories: 1) performing loans; 2) 30 to 89 days past due loans; and 3) non-accrual and ninety days or more past due loans. The primary credit quality indicator for commercial real estate and commercial loans is the Company’s internal risk rating system, which includes the following categories: 1) pass loans; 2) special mention loans; 3) substandard loans; and 4) doubtful or loss loans. Such credit quality indicators are regularly monitored and incorporated into the Company’s allowance estimate. The following paragraphs further define the internal risk ratings for commercial real estate and commercial loans. </span></div><div><span><br/></span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-style:italic;font-weight:400;line-height:120%">Pass Loans.</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%"> These ratings represent loans that are of acceptable, good or excellent quality with very limited to no risk. Loans that do not have one of the following ratings are considered pass loans. </span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-style:italic;font-weight:400;line-height:120%">Special Mention Loans.</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%"> These ratings represent loans that are designated as special mention per the regulatory definition. Special mention loans are currently protected but are potentially weak. The credit risk may be relatively minor yet constitute an undue and unwarranted risk in light of the circumstances surrounding a specific loan. The rating may be used to identify credit with potential weaknesses that if not corrected may weaken the loan to the point of inadequately protecting the Bank’s credit position. Examples include a lack of supervision, inadequate loan agreement, condition, or control of collateral, incomplete, or improper documentation, deviations from lending policy, and adverse trends in operations or economic conditions.</span></div><div><span><br/></span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-style:italic;font-weight:400;line-height:120%">Substandard Loans. </span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%"> This rating represents loans that are inadequately protected by the current sound worth and paying capacity of the obligor or of the collateral pledged. A loan so classified must have a well-defined weakness that jeopardizes the liquidation of the debt. These loans are characterized by the distinct possibility that the Bank will sustain some loss if the deficiencies are not corrected. Loss potential, while existing in the aggregated amount of substandard loans, does not have to exist in an individual loan classified substandard.</span></div><div style="text-align:justify"><span><br/></span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-style:italic;font-weight:400;line-height:120%">Doubtful/Loss Loans. </span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%"> A loan classified as doubtful has the characteristics that make collection in full, on the basis of currently existing facts, conditions, and values, highly improbable. The possibility of loss is extremely high, but because of pending factors, which may work to the advantage and strengthening of the loan, its classification as loss is deferred until its more exact status may be determined. Pending factors include proposed merger, acquisition, or liquidation procedures, capital injection, perfecting liens on additional collateral and refinancing plans. Loans are classified as loss when they are deemed to be not collectible and of such little value that continuance as an active asset of the Bank is not warranted. Loans classified as loss must be charged-off. Assignment of this classification does not mean that an asset has absolutely no recovery or salvage value, but that it is not practical or desirable to defer writing off a basically worthless asset, even though partial recovery may be attained in the future.</span></div><div style="text-align:justify"><span><br/></span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%;text-decoration:underline">Restructured Loans</span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">A restructured loan is considered a troubled debt restructuring (“TDR”) if the creditor, for economic or legal reasons related to the debtor’s financial difficulties, grants a concession to the debtor that it would not otherwise consider. The Company periodically enters into restructure agreements with borrowers whereby the loans were previously identified as TDRs. When such circumstances occur, the Company carefully evaluates the facts of the subsequent restructure to determine the appropriate accounting and under certain circumstances it may be acceptable not to account for the subsequently restructured loan as a TDR. When assessing whether a concession has been granted by the Company, any prior forgiveness on a cumulative basis is considered a continuing concession. The Company has made the following types of loan modifications, some of which were considered a TDR:</span></div><div style="margin-top:6pt;padding-left:36pt;text-indent:-18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:14.5pt">reduction of the stated interest rate for the remaining term of the debt;</span></div><div style="padding-left:36pt;text-indent:-18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:14.5pt">extension of the maturity date(s) at a stated rate of interest lower than the current market rate for newly originated debt having similar risk characteristics; and</span></div><div style="padding-left:36pt;text-indent:-18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:14.5pt">reduction of the face amount of the debt as stated in the debt agreements.</span></div><div style="text-align:justify"><span><br/></span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">The Company recognizes that while borrowers may experience deterioration in their financial condition, many continue to be creditworthy borrowers who have the willingness and capacity for debt repayment. In determining whether non-restructured or performing loans issued to a single or related party group of borrowers should continue to accrue interest when the borrower has other loans that are non-performing or are TDRs, the Company, on a quarterly or more frequent basis, performs an updated and comprehensive assessment of the willingness and capacity of the borrowers to timely and ultimately repay their total debt obligations, including contingent obligations. Such analysis takes into account current financial information about the borrowers and financially responsible guarantors, if any, including for example:</span></div><div style="margin-top:6pt;padding-left:36pt;text-indent:-18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:14.5pt">analysis of global, i.e., aggregate debt service for total debt obligations;</span></div><div style="padding-left:36pt;text-align:justify;text-indent:-18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:14.5pt">assessment of the value and security protection of collateral pledged using current market conditions and alternative market assumptions across a variety of potential future situations; and</span></div><div style="padding-left:36pt;text-indent:-18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:14.5pt">loan structures and related covenants.</span></div><div style="padding-left:36pt"><span><br/></span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">On March 27, 2020, the Coronavirus Aid, Relief, and Economic Security Act (“CARES Act”) was signed into law which includes many provisions that impact the Company and its customers. The banking regulatory agencies have encouraged banks to work with borrowers who have been impacted by the coronavirus disease of 2019 (“COVID-19”) and the CARES Act, along with related regulatory guidance, allows banks to not designate certain modifications as TDRs that otherwise may have been classified as TDRs. In general, in order to qualify for such treatment, the modifications need to be short-term and made on a good faith basis in response to the COVID-19 pandemic to borrowers who were previously deemed current as outlined in the regulatory guidance. The Company has made such modifications to assist borrowers impacted by the COVID-19 pandemic. </span></div><div style="text-align:justify"><span><br/></span></div><div style="text-align:justify"><span style="background-color:#ffffff;color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">The allowance for credit losses on a TDR is measured using the same method as all other loans held for investment. For a TDR that is individually reviewed and not collateral-dependent, the value of the concession can only be measured using the discounted cash flow method. When the value of a </span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">concession is measured using the discounted cash flow method, the ACL is determined by discounting the expected future cash flows at the original interest of the loan.</span></div><div style="margin-top:6pt;text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%;text-decoration:underline">Allowance for Credit Losses - Off-Balance Sheet Credit Exposures</span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">The Company maintains a separate allowance for off-balance sheet credit exposures, including unfunded loan commitments, which is included in other liabilities on the Company’s statements of financial condition. The Company estimates the amount of expected losses by calculating a commitment usage factor over the contractual period for exposures and applying the loss factors used in the allowance for credit loss methodology to the results of the usage calculation to estimate the liability for credit losses related to unfunded commitments for each loan segment. No credit loss estimate is reported for off-balance sheet credit exposures that are unconditionally cancellable by the Bank or for unfunded amounts under such arrangements that may be drawn prior to the cancellation of the arrangement. </span></div><div style="text-align:justify"><span><br/></span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%;text-decoration:underline">Provision for Credit Losses</span></div>The Company recognizes provision for credit losses on the allowance for off-balance sheet credit exposures (e.g., unfunded loan commitments) together with provision for credit losses on the loan portfolio in the income statement line item provision for credit losses. Provision for credit losses on the loan portfolio and for off-balance sheet credit exposures were $37,637,000 and $2,128,000 for the year ended December 31, 2020, respectively. There was no provision for credit losses on debt securities for the year ended December 31, 2020, respectively.
CY2020	gbci	Financing Receivable Allowance For Credit Losses Forecasting Period FinancingReceivableAllowanceForCreditLossesForecastingPeriod	4	quarter
CY2020	gbci	Financing Receivable Allowance For Credit Losses Forecasting Period FinancingReceivableAllowanceForCreditLossesForecastingPeriod	4	quarter
CY2020	gbci	Financing Receivable Allowance For Credit Losses Number Of Components FinancingReceivableAllowanceForCreditLossesNumberOfComponents	2	numberOfComponents
CY2020	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	37637000	USD
CY2020	us-gaap	Provision For Other Credit Losses ProvisionForOtherCreditLosses	2128000	USD
CY2020	gbci	Maximum Term Leases Will Be Considered Short Term MaximumTermLeasesWillBeConsideredShortTerm	P12M
CY2020	gbci	Maximum Period Up To Which Purchase Price Of Business Is Allocated To Assets Acquired And Liabilities Assumed MaximumPeriodUpToWhichPurchasePriceOfBusinessIsAllocatedToAssetsAcquiredAndLiabilitiesAssumed	P1Y
CY2020	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	54520000	USD
CY2019	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	69877000	USD
CY2018	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	76664000	USD
CY2020Q4	us-gaap	Capitalized Contract Cost Accumulated Impairment CapitalizedContractCostAccumulatedImpairment	0	USD
CY2019Q4	us-gaap	Capitalized Contract Cost Accumulated Impairment CapitalizedContractCostAccumulatedImpairment	0	USD
CY2020	gbci	Percentage Of Likelihood For Term More Likely Than Not PercentageOfLikelihoodForTermMoreLikelyThanNot	0.50
CY2020	us-gaap	Prior Period Reclassification Adjustment Description PriorPeriodReclassificationAdjustmentDescription	<div><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%;text-decoration:underline">Reclassifications</span></div><div><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">Certain reclassifications have been made to the 2019 and 2018 financial statements to conform to the 2020 presentation.</span></div>
CY2020Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	5145866000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	192740000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	792000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	5337814000	USD
CY2020Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	189836000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	13380000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Loss HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	0	USD
CY2020Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	203216000	USD
CY2020Q4	gbci	Debt Securities Amortized Cost Basis DebtSecuritiesAmortizedCostBasis	5335702000	USD
CY2020Q4	gbci	Securities Gross Unrealized Gain Accumulated In Investments SecuritiesGrossUnrealizedGainAccumulatedInInvestments	206120000	USD
CY2020Q4	gbci	Securities Gross Unrealized Loss Accumulated In Investments1 SecuritiesGrossUnrealizedLossAccumulatedInInvestments1	792000	USD
CY2020Q4	gbci	Debt Securities Fair Value DebtSecuritiesFairValue	5541030000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	2521374000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	55965000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	2087000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	2575252000	USD
CY2019Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	224611000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	9785000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Loss HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	0	USD
CY2019Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	234396000	USD
CY2019Q4	gbci	Debt Securities Amortized Cost Basis DebtSecuritiesAmortizedCostBasis	2745985000	USD
CY2019Q4	gbci	Securities Gross Unrealized Gain Accumulated In Investments SecuritiesGrossUnrealizedGainAccumulatedInInvestments	65750000	USD
CY2019Q4	gbci	Securities Gross Unrealized Loss Accumulated In Investments1 SecuritiesGrossUnrealizedLossAccumulatedInInvestments1	2087000	USD
CY2019Q4	gbci	Debt Securities Fair Value DebtSecuritiesFairValue	2809648000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities Next Rolling Twelve Months Amortized Cost Basis AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsAmortizedCostBasis	128263000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities Next Rolling Twelve Months Fair Value AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsFairValue	129346000	USD
CY2020Q4	us-gaap	Heldtomaturity Securities Debt Maturities Next Rolling Twelve Months Amortized Cost HeldtomaturitySecuritiesDebtMaturitiesNextRollingTwelveMonthsAmortizedCost	484000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities Next Rolling Twelve Months Fair Value HeldToMaturitySecuritiesDebtMaturitiesNextRollingTwelveMonthsFairValue	489000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities Rolling Year Two Through Five Amortized Cost Basis AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughFiveAmortizedCostBasis	246473000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities Rolling Year Two Through Five Fair Value AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughFiveFairValue	258040000	USD
CY2020Q4	us-gaap	Heldtomaturity Securities Debt Maturities Rolling Year Two Through Five Amortized Cost HeldtomaturitySecuritiesDebtMaturitiesRollingYearTwoThroughFiveAmortizedCost	22032000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities Rolling Year Two Through Five Fair Value HeldToMaturitySecuritiesDebtMaturitiesRollingYearTwoThroughFiveFairValue	23625000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities Rolling Year Six Through Ten Amortized Cost Basis AvailableForSaleSecuritiesDebtMaturitiesRollingYearSixThroughTenAmortizedCostBasis	266248000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities Rolling Year Six Through Ten Fair Value AvailableForSaleSecuritiesDebtMaturitiesRollingYearSixThroughTenFairValue	280021000	USD
CY2020Q4	us-gaap	Heldtomaturity Securities Debt Maturities Rolling Year Six Through Ten Amortized Cost HeldtomaturitySecuritiesDebtMaturitiesRollingYearSixThroughTenAmortizedCost	67678000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities Rolling Year Six Through Ten Fair Value HeldToMaturitySecuritiesDebtMaturitiesRollingYearSixThroughTenFairValue	73367000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities Rolling After Year Ten Amortized Cost Basis AvailableForSaleSecuritiesDebtMaturitiesRollingAfterYearTenAmortizedCostBasis	1065961000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities Rolling After Year Ten Fair Value AvailableForSaleSecuritiesDebtMaturitiesRollingAfterYearTenFairValue	1146743000	USD
CY2020Q4	us-gaap	Heldtomaturity Securities Debt Maturities Rolling After Ten Years Amortized Cost HeldtomaturitySecuritiesDebtMaturitiesRollingAfterTenYearsAmortizedCost	99642000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities Rolling After Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesRollingAfterTenYearsFairValue	105735000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities Single Maturity Date Amortized Cost Basis AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis	1706945000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities Single Maturity Date AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDate	1814150000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities Single Maturity Date Amortized Cost Basis HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis	189836000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities Single Maturity Date Fair Value HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateFairValue	203216000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	5145866000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	5337814000	USD
CY2020Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	189836000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	203216000	USD
CY2020	gbci	Proceeds From Sales And Calls Of Debt Securities Available For Sale ProceedsFromSalesAndCallsOfDebtSecuritiesAvailableForSale	240521000	USD
CY2019	gbci	Proceeds From Sales And Calls Of Debt Securities Available For Sale ProceedsFromSalesAndCallsOfDebtSecuritiesAvailableForSale	928710000	USD
CY2018	gbci	Proceeds From Sales And Calls Of Debt Securities Available For Sale ProceedsFromSalesAndCallsOfDebtSecuritiesAvailableForSale	265587000	USD
CY2020	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	1400000	USD
CY2019	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	18936000	USD
CY2018	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	443000	USD
CY2020	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	262000	USD
CY2019	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	4513000	USD
CY2018	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	455000	USD
CY2020	gbci	Held To Maturity Securities Gross Realized Gains Losses Sale Proceeds HeldToMaturitySecuritiesGrossRealizedGainsLossesSaleProceeds	32735000	USD
CY2019	gbci	Held To Maturity Securities Gross Realized Gains Losses Sale Proceeds HeldToMaturitySecuritiesGrossRealizedGainsLossesSaleProceeds	58750000	USD
CY2018	gbci	Held To Maturity Securities Gross Realized Gains Losses Sale Proceeds HeldToMaturitySecuritiesGrossRealizedGainsLossesSaleProceeds	79000000	USD
CY2020	gbci	Held To Maturity Securities Sold Security Realized Gain HeldToMaturitySecuritiesSoldSecurityRealizedGain	1000	USD
CY2019	gbci	Held To Maturity Securities Sold Security Realized Gain HeldToMaturitySecuritiesSoldSecurityRealizedGain	2000	USD
CY2018	gbci	Held To Maturity Securities Sold Security Realized Gain HeldToMaturitySecuritiesSoldSecurityRealizedGain	101000	USD
CY2020	gbci	Held To Maturity Securities Sold Security Realized Loss HeldToMaturitySecuritiesSoldSecurityRealizedLoss	0	USD
CY2019	gbci	Held To Maturity Securities Sold Security Realized Loss HeldToMaturitySecuritiesSoldSecurityRealizedLoss	10000	USD
CY2018	gbci	Held To Maturity Securities Sold Security Realized Loss HeldToMaturitySecuritiesSoldSecurityRealizedLoss	1202000	USD
CY2020Q4	us-gaap	Security Owned And Pledged As Collateral Fair Value SecurityOwnedAndPledgedAsCollateralFairValue	2169967000	USD
CY2019Q4	us-gaap	Security Owned And Pledged As Collateral Fair Value SecurityOwnedAndPledgedAsCollateralFairValue	1475752000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Number Of Positions DebtSecuritiesAvailableForSaleUnrealizedLossPositionNumberOfPositions	46	security
CY2020Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months	145530000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	783000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger	753000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	9000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position DebtSecuritiesAvailableForSaleUnrealizedLossPosition	146283000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Accumulated Loss DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss	792000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Number Of Positions DebtSecuritiesAvailableForSaleUnrealizedLossPositionNumberOfPositions	88	security
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months	289499000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	1608000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger	46637000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	479000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position DebtSecuritiesAvailableForSaleUnrealizedLossPosition	336136000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Accumulated Loss DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss	2087000	USD
CY2020	gbci	Available For Sale Securities In Unrealized Loss Positions Severity Rate AvailableForSaleSecuritiesInUnrealizedLossPositionsSeverityRate	0.05
CY2020Q4	gbci	Number Of Credit Rating Categories Highest NumberOfCreditRatingCategoriesHighest	4	security
CY2020Q4	gbci	Interest Receivable Available For Sale Debt Securities InterestReceivableAvailableForSaleDebtSecurities	20215000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	0	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	0	USD
CY2020Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	189836000	USD
CY2019Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	224611000	USD
CY2020Q4	gbci	Number Of Credit Rating Categories Highest NumberOfCreditRatingCategoriesHighest	4	security
CY2020Q4	gbci	Interest Receivable Held To Maturity Debt Securities InterestReceivableHeldToMaturityDebtSecurities	1728000	USD
CY2020Q4	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss DebtSecuritiesHeldToMaturityAllowanceForCreditLoss	0	USD
CY2020Q4	us-gaap	Notes Receivable Gross NotesReceivableGross	11122696000	USD
CY2019Q4	us-gaap	Notes Receivable Gross NotesReceivableGross	9512810000	USD
CY2020Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	158243000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	124490000	USD
CY2020Q4	us-gaap	Notes Receivable Net NotesReceivableNet	10964453000	USD
CY2019Q4	us-gaap	Notes Receivable Net NotesReceivableNet	9388320000	USD
CY2020Q4	gbci	Unamortized Loan Origination Fees And Costs UnamortizedLoanOriginationFeesAndCosts	-26709000	USD
CY2019Q4	gbci	Unamortized Loan Origination Fees And Costs UnamortizedLoanOriginationFeesAndCosts	-6964000	USD
CY2020Q4	gbci	Unamortized Discounts And Premiums On Loans UnamortizedDiscountsAndPremiumsOnLoans	-17091000	USD
CY2019Q4	gbci	Unamortized Discounts And Premiums On Loans UnamortizedDiscountsAndPremiumsOnLoans	-21574000	USD
CY2020Q4	gbci	Interest Receivable Financing Receivable InterestReceivableFinancingReceivable	53538000	USD
CY2019Q4	gbci	Interest Receivable Financing Receivable InterestReceivableFinancingReceivable	40962000	USD
CY2020Q4	us-gaap	Loans Pledged As Collateral LoansPledgedAsCollateral	6707315000	USD
CY2020Q4	gbci	Percentage Of Consolidated Stockholders Equity Exceeding Which No Borrower Had Outstanding Loans Or Commitments PercentageOfConsolidatedStockholdersEquityExceedingWhichNoBorrowerHadOutstandingLoansOrCommitments	0.10
CY2020Q4	us-gaap	Notes Receivable Related Parties NotesReceivableRelatedParties	77634000	USD
CY2019Q4	us-gaap	Notes Receivable Related Parties NotesReceivableRelatedParties	57825000	USD
CY2020	us-gaap	Origination Of Notes Receivable From Related Parties OriginationOfNotesReceivableFromRelatedParties	35242000	USD
CY2020	us-gaap	Repayment Of Notes Receivable From Related Parties RepaymentOfNotesReceivableFromRelatedParties	15432000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	124490000	USD
CY2020	us-gaap	Financing Receivable Change In Method Credit Loss Expense Reversal FinancingReceivableChangeInMethodCreditLossExpenseReversal	3720000	USD
CY2020	us-gaap	Financing Receivable Allowance For Credit Loss Purchased With Credit Deterioration Increase FinancingReceivableAllowanceForCreditLossPurchasedWithCreditDeteriorationIncrease	49000	USD
CY2020	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	37637000	USD
CY2020	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	13808000	USD
CY2020	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	6155000	USD
CY2020Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	158243000	USD
CY2018Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	131239000	USD
CY2019	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	57000	USD
CY2019	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	15178000	USD
CY2019	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	8372000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	124490000	USD
CY2017Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	129568000	USD
CY2018	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	9953000	USD
CY2018	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	17807000	USD
CY2018	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	9525000	USD
CY2018Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	131239000	USD
CY2020	us-gaap	Financing Receivable Purchased With Credit Deterioration Amount At Par Value FinancingReceivablePurchasedWithCreditDeteriorationAmountAtParValue	3401000	USD
CY2020	us-gaap	Financing Receivable Purchased With Credit Deterioration Allowance For Credit Loss At Acquisition Date FinancingReceivablePurchasedWithCreditDeteriorationAllowanceForCreditLossAtAcquisitionDate	49000	USD
CY2020	us-gaap	Financing Receivable Purchased With Credit Deterioration Discount Premium FinancingReceivablePurchasedWithCreditDeteriorationDiscountPremium	13000	USD
CY2020Q4	us-gaap	Financing Receivable Nonaccrual No Allowance FinancingReceivableNonaccrualNoAllowance	29532000	USD
CY2020Q4	gbci	Financing Receivable Nonaccrual With Allowance FinancingReceivableNonaccrualWithAllowance	2432000	USD
CY2020Q4	gbci	Financing Receivable Recorded Investment Past Due And Non Accrual Loans FinancingReceivableRecordedInvestmentPastDueAndNonAccrualLoans	56410000	USD
CY2020Q4	us-gaap	Financing Receivable Recorded Investment Current FinancingReceivableRecordedInvestmentCurrent	11066286000	USD
CY2020Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	11122696000	USD
CY2019Q4	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	30883000	USD
CY2019Q4	gbci	Financing Receivable Recorded Investment Past Due And Non Accrual Loans FinancingReceivableRecordedInvestmentPastDueAndNonAccrualLoans	55487000	USD
CY2019Q4	us-gaap	Financing Receivable Recorded Investment Current FinancingReceivableRecordedInvestmentCurrent	9457323000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	9512810000	USD
CY2020	gbci	Financing Receivable Nonaccrual Interest Income Reversed FinancingReceivableNonaccrualInterestIncomeReversed	832000	USD
CY2020Q4	gbci	Collateral Dependent Loans CollateralDependentLoans	64455000	USD
CY2020	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	16	Loan
CY2020	us-gaap	Financing Receivable Modifications Pre Modification Recorded Investment2 FinancingReceivableModificationsPreModificationRecordedInvestment2	14945000	USD
CY2020	us-gaap	Financing Receivable Modifications Post Modification Recorded Investment2 FinancingReceivableModificationsPostModificationRecordedInvestment2	14945000	USD
CY2020	us-gaap	Financing Receivable Modifications Subsequent Default Number Of Contracts1 FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1	1	Loan
CY2020	us-gaap	Financing Receivable Modifications Subsequent Default Recorded Investment1 FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1	145000	USD
CY2019	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	18	Loan
CY2019	us-gaap	Financing Receivable Modifications Pre Modification Recorded Investment2 FinancingReceivableModificationsPreModificationRecordedInvestment2	18508000	USD
CY2019	us-gaap	Financing Receivable Modifications Post Modification Recorded Investment2 FinancingReceivableModificationsPostModificationRecordedInvestment2	18476000	USD
CY2019	us-gaap	Financing Receivable Modifications Subsequent Default Number Of Contracts1 FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1	1	Loan
CY2019	us-gaap	Financing Receivable Modifications Subsequent Default Recorded Investment1 FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1	106000	USD
CY2018	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	25	Loan
CY2018	us-gaap	Financing Receivable Modifications Pre Modification Recorded Investment2 FinancingReceivableModificationsPreModificationRecordedInvestment2	21995000	USD
CY2018	us-gaap	Financing Receivable Modifications Post Modification Recorded Investment2 FinancingReceivableModificationsPostModificationRecordedInvestment2	21881000	USD
CY2018	us-gaap	Financing Receivable Modifications Subsequent Default Number Of Contracts1 FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1	1	Loan
CY2018	us-gaap	Financing Receivable Modifications Subsequent Default Recorded Investment1 FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1	47000	USD
CY2020Q4	gbci	Tdr With Pre Modification Loan Balance For Which Oreo Was Received TDRWithPreModificationLoanBalanceForWhichOreoWasReceived	2278000	USD
CY2019Q4	gbci	Tdr With Pre Modification Loan Balance For Which Oreo Was Received TDRWithPreModificationLoanBalanceForWhichOreoWasReceived	2992000	USD
CY2018Q4	gbci	Tdr With Pre Modification Loan Balance For Which Oreo Was Received TDRWithPreModificationLoanBalanceForWhichOreoWasReceived	6793000	USD
CY2020Q4	us-gaap	Mortgage Loans In Process Of Foreclosure Amount MortgageLoansInProcessOfForeclosureAmount	548000	USD
CY2019Q4	us-gaap	Mortgage Loans In Process Of Foreclosure Amount MortgageLoansInProcessOfForeclosureAmount	1744000	USD
CY2020Q4	gbci	Real Estate Acquired Through Foreclosure Secured By Residential Real Estate RealEstateAcquiredThroughForeclosureSecuredByResidentialRealEstate	273000	USD
CY2019Q4	gbci	Real Estate Acquired Through Foreclosure Secured By Residential Real Estate RealEstateAcquiredThroughForeclosureSecuredByResidentialRealEstate	1504000	USD
CY2020Q4	gbci	Additional Outstanding Commitments On Troubled Debt Restructuring AdditionalOutstandingCommitmentsOnTroubledDebtRestructuring	817000	USD
CY2019Q4	gbci	Additional Outstanding Commitments On Troubled Debt Restructuring AdditionalOutstandingCommitmentsOnTroubledDebtRestructuring	3933000	USD
CY2020	us-gaap	Financing Receivables Impaired Troubled Debt Restructuring Write Down FinancingReceivablesImpairedTroubledDebtRestructuringWriteDown	453000	USD
CY2019	us-gaap	Financing Receivables Impaired Troubled Debt Restructuring Write Down FinancingReceivablesImpairedTroubledDebtRestructuringWriteDown	709000	USD
CY2018	us-gaap	Financing Receivables Impaired Troubled Debt Restructuring Write Down FinancingReceivablesImpairedTroubledDebtRestructuringWriteDown	1685000	USD
CY2019Q4	us-gaap	Financing Receivable Individually Evaluated For Impairment FinancingReceivableIndividuallyEvaluatedForImpairment	94504000	USD
CY2019Q4	us-gaap	Financing Receivable Collectively Evaluated For Impairment FinancingReceivableCollectivelyEvaluatedForImpairment	9418306000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	9512810000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses Individually Evaluated For Impairment1 FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1	95000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses Collectively Evaluated For Impairment FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment	124395000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	124490000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable With Related Allowance Recorded Investment ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment	5388000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable With Related Allowance Unpaid Principal Balance ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance	5388000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable Related Allowance ImpairedFinancingReceivableRelatedAllowance	95000	USD
CY2019	us-gaap	Impaired Financing Receivable With Related Allowance Average Recorded Investment ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment	10378000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable With No Related Allowance Recorded Investment ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment	89116000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable With No Related Allowance Unpaid Principal Balance ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance	99355000	USD
CY2019	us-gaap	Impaired Financing Receivable With No Related Allowance Average Recorded Investment ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment	93338000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable Recorded Investment ImpairedFinancingReceivableRecordedInvestment	94504000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable Unpaid Principal Balance ImpairedFinancingReceivableUnpaidPrincipalBalance	104743000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable Related Allowance ImpairedFinancingReceivableRelatedAllowance	95000	USD
CY2019	us-gaap	Impaired Financing Receivable Average Recorded Investment ImpairedFinancingReceivableAverageRecordedInvestment	103716000	USD
CY2020Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	159555000	USD
CY2019Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	148373000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	272789000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	263236000	USD
CY2020Q4	gbci	Right Of Use Asset RightOfUseAsset	52546000	USD
CY2019Q4	gbci	Right Of Use Asset RightOfUseAsset	47073000	USD
CY2020Q4	us-gaap	Property Plant And Equipment And Finance Lease Right Of Use Asset After Accumulated Depreciation And Amortization PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization	325335000	USD
CY2019Q4	us-gaap	Property Plant And Equipment And Finance Lease Right Of Use Asset After Accumulated Depreciation And Amortization PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization	310309000	USD
CY2020Q4	us-gaap	Finance Lease Right Of Use Asset Before Accumulated Amortization FinanceLeaseRightOfUseAssetBeforeAccumulatedAmortization	5999000	USD
CY2019Q4	us-gaap	Finance Lease Right Of Use Asset Before Accumulated Amortization FinanceLeaseRightOfUseAssetBeforeAccumulatedAmortization	6537000	USD
CY2020Q4	us-gaap	Finance Lease Right Of Use Asset Accumulated Amortization FinanceLeaseRightOfUseAssetAccumulatedAmortization	273000	USD
CY2019Q4	us-gaap	Finance Lease Right Of Use Asset Accumulated Amortization FinanceLeaseRightOfUseAssetAccumulatedAmortization	917000	USD
CY2020Q4	us-gaap	Finance Lease Right Of Use Asset FinanceLeaseRightOfUseAsset	5726000	USD
CY2020Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	46820000	USD
CY2019Q4	us-gaap	Finance Lease Right Of Use Asset FinanceLeaseRightOfUseAsset	5620000	USD
CY2019Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	41453000	USD
CY2020Q4	us-gaap	Finance Lease Liability FinanceLeaseLiability	5891000	USD
CY2020Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	49675000	USD
CY2019Q4	us-gaap	Finance Lease Liability FinanceLeaseLiability	5671000	USD
CY2019Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	43904000	USD
CY2020Q4	us-gaap	Finance Lease Weighted Average Remaining Lease Term1 FinanceLeaseWeightedAverageRemainingLeaseTerm1	P24Y
CY2020Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P17Y
CY2019Q4	us-gaap	Finance Lease Weighted Average Remaining Lease Term1 FinanceLeaseWeightedAverageRemainingLeaseTerm1	P24Y
CY2019Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P19Y
CY2020Q4	us-gaap	Finance Lease Weighted Average Discount Rate Percent FinanceLeaseWeightedAverageDiscountRatePercent	0.026
CY2020Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.034
CY2019Q4	us-gaap	Finance Lease Weighted Average Discount Rate Percent FinanceLeaseWeightedAverageDiscountRatePercent	0.030
CY2019Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.037
CY2020Q4	us-gaap	Finance Lease Liability Payments Due In Next Rolling Twelve Months FinanceLeaseLiabilityPaymentsDueInNextRollingTwelveMonths	260000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Next Rolling Twelve Months LesseeOperatingLeaseLiabilityPaymentsDueNextRollingTwelveMonths	4639000	USD
CY2020Q4	us-gaap	Finance Lease Liability Payments Due In Rolling Year Two FinanceLeaseLiabilityPaymentsDueInRollingYearTwo	266000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due In Rolling Year Two LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearTwo	4407000	USD
CY2020Q4	us-gaap	Finance Lease Liability Payments Due In Rolling Year Three FinanceLeaseLiabilityPaymentsDueInRollingYearThree	272000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due In Rolling Year Three LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearThree	3979000	USD
CY2020Q4	us-gaap	Finance Lease Liability Payments Due In Rolling Year Four FinanceLeaseLiabilityPaymentsDueInRollingYearFour	280000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due In Rolling Year Four LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearFour	3987000	USD
CY2020Q4	us-gaap	Finance Lease Liability Payments Due In Rolling Year Five FinanceLeaseLiabilityPaymentsDueInRollingYearFive	285000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due In Rolling Year Five LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearFive	3932000	USD
CY2020Q4	us-gaap	Finance Lease Liability Payments Due In Rolling After Year Five FinanceLeaseLiabilityPaymentsDueInRollingAfterYearFive	6736000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due After Rolling Year Five LesseeOperatingLeaseLiabilityPaymentsDueAfterRollingYearFive	47434000	USD
CY2020Q4	us-gaap	Finance Lease Liability Payments Due FinanceLeaseLiabilityPaymentsDue	8099000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	68378000	USD
CY2020Q4	us-gaap	Finance Lease Liability Current FinanceLeaseLiabilityCurrent	109000	USD
CY2020Q4	us-gaap	Operating Lease Liability Current OperatingLeaseLiabilityCurrent	3023000	USD
CY2020Q4	us-gaap	Finance Lease Liability Noncurrent FinanceLeaseLiabilityNoncurrent	5782000	USD
CY2020Q4	us-gaap	Operating Lease Liability Noncurrent OperatingLeaseLiabilityNoncurrent	46652000	USD
CY2020Q4	us-gaap	Finance Lease Liability FinanceLeaseLiability	5891000	USD
CY2020Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	49675000	USD
CY2020Q4	us-gaap	Finance Lease Liability Undiscounted Excess Amount FinanceLeaseLiabilityUndiscountedExcessAmount	2208000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	18703000	USD
CY2020	us-gaap	Finance Lease Right Of Use Asset Amortization FinanceLeaseRightOfUseAssetAmortization	235000	USD
CY2019	us-gaap	Finance Lease Right Of Use Asset Amortization FinanceLeaseRightOfUseAssetAmortization	101000	USD
CY2020	us-gaap	Finance Lease Interest Expense FinanceLeaseInterestExpense	159000	USD
CY2019	us-gaap	Finance Lease Interest Expense FinanceLeaseInterestExpense	34000	USD
CY2020	us-gaap	Operating Lease Cost OperatingLeaseCost	4807000	USD
CY2019	us-gaap	Operating Lease Cost OperatingLeaseCost	4063000	USD
CY2020	us-gaap	Short Term Lease Cost ShortTermLeaseCost	331000	USD
CY2019	us-gaap	Short Term Lease Cost ShortTermLeaseCost	431000	USD
CY2020	us-gaap	Variable Lease Cost VariableLeaseCost	1270000	USD
CY2019	us-gaap	Variable Lease Cost VariableLeaseCost	896000	USD
CY2020	us-gaap	Sublease Income SubleaseIncome	12000	USD
CY2019	us-gaap	Sublease Income SubleaseIncome	6000	USD
CY2020	us-gaap	Lease Cost LeaseCost	6790000	USD
CY2019	us-gaap	Lease Cost LeaseCost	5519000	USD
CY2020	us-gaap	Finance Lease Interest Payment On Liability FinanceLeaseInterestPaymentOnLiability	159000	USD
CY2020	us-gaap	Operating Lease Payments OperatingLeasePayments	2742000	USD
CY2019	us-gaap	Finance Lease Interest Payment On Liability FinanceLeaseInterestPaymentOnLiability	34000	USD
CY2019	us-gaap	Operating Lease Payments OperatingLeasePayments	2136000	USD
CY2020	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	93000	USD
CY2019	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	98000	USD
CY2019Q4	us-gaap	Goodwill Goodwill	456418000	USD
CY2018Q4	us-gaap	Goodwill Goodwill	289586000	USD
CY2017Q4	us-gaap	Goodwill Goodwill	177811000	USD
CY2020	us-gaap	Goodwill Acquired During Period GoodwillAcquiredDuringPeriod	57595000	USD
CY2019	us-gaap	Goodwill Acquired During Period GoodwillAcquiredDuringPeriod	166832000	USD
CY2018	us-gaap	Goodwill Acquired During Period GoodwillAcquiredDuringPeriod	111775000	USD
CY2020Q4	us-gaap	Goodwill Goodwill	514013000	USD
CY2019Q4	us-gaap	Goodwill Goodwill	456418000	USD
CY2018Q4	us-gaap	Goodwill Goodwill	289586000	USD
CY2020Q4	us-gaap	Goodwill Impaired Accumulated Impairment Loss GoodwillImpairedAccumulatedImpairmentLoss	40159000	USD
CY2019Q4	us-gaap	Goodwill Impaired Accumulated Impairment Loss GoodwillImpairedAccumulatedImpairmentLoss	40159000	USD
CY2020Q4	us-gaap	Servicing Asset ServicingAsset	1269080000	USD
CY2019Q4	us-gaap	Servicing Asset ServicingAsset	185897000	USD
CY2020Q4	us-gaap	Servicing Asset At Fair Value Amount ServicingAssetAtFairValueAmount	12086921	USD
CY2019Q4	us-gaap	Servicing Asset At Fair Value Amount ServicingAssetAtFairValueAmount	1763144	USD
CY2019Q4	us-gaap	Servicing Asset At Amortized Value ServicingAssetAtAmortizedValue	1618000	USD
CY2018Q4	us-gaap	Servicing Asset At Amortized Value ServicingAssetAtAmortizedValue	1545000	USD
CY2017Q4	us-gaap	Servicing Asset At Amortized Value ServicingAssetAtAmortizedValue	0	USD
CY2020	gbci	Servicing Asset At Amortized Cost Acquisitions ServicingAssetAtAmortizedCostAcquisitions	0	USD
CY2019	gbci	Servicing Asset At Amortized Cost Acquisitions ServicingAssetAtAmortizedCostAcquisitions	0	USD
CY2018	gbci	Servicing Asset At Amortized Cost Acquisitions ServicingAssetAtAmortizedCostAcquisitions	1689000	USD
CY2020	us-gaap	Servicing Asset At Amortized Value Additions ServicingAssetAtAmortizedValueAdditions	8298000	USD
CY2019	us-gaap	Servicing Asset At Amortized Value Additions ServicingAssetAtAmortizedValueAdditions	325000	USD
CY2018	us-gaap	Servicing Asset At Amortized Value Additions ServicingAssetAtAmortizedValueAdditions	28000	USD
CY2020	us-gaap	Servicing Asset At Amortized Value Amortization1 ServicingAssetAtAmortizedValueAmortization1	940000	USD
CY2019	us-gaap	Servicing Asset At Amortized Value Amortization1 ServicingAssetAtAmortizedValueAmortization1	252000	USD
CY2018	us-gaap	Servicing Asset At Amortized Value Amortization1 ServicingAssetAtAmortizedValueAmortization1	172000	USD
CY2020Q4	us-gaap	Servicing Asset At Amortized Value ServicingAssetAtAmortizedValue	8976000	USD
CY2019Q4	us-gaap	Servicing Asset At Amortized Value ServicingAssetAtAmortizedValue	1618000	USD
CY2018Q4	us-gaap	Servicing Asset At Amortized Value ServicingAssetAtAmortizedValue	1545000	USD
CY2019Q4	us-gaap	Pledged Financial Instruments Not Separately Reported Securities For Repurchase Agreements PledgedFinancialInstrumentsNotSeparatelyReportedSecuritiesForRepurchaseAgreements	711210000	USD
CY2020Q4	us-gaap	Cash Fdic Insured Amount CashFDICInsuredAmount	250000	USD
CY2020Q4	gbci	Time Deposits That Meet Or Exceed Fdic Insurance Limit TimeDepositsThatMeetOrExceedFDICInsuranceLimit	297975000	USD
CY2019Q4	gbci	Time Deposits That Meet Or Exceed Fdic Insurance Limit TimeDepositsThatMeetOrExceedFDICInsuranceLimit	281054000	USD
CY2020Q4	us-gaap	Time Deposit Maturities Year One TimeDepositMaturitiesYearOne	707026000	USD
CY2020Q4	us-gaap	Time Deposit Maturities Year Two TimeDepositMaturitiesYearTwo	134255000	USD
CY2020Q4	us-gaap	Time Deposit Maturities Year Three TimeDepositMaturitiesYearThree	50948000	USD
CY2020Q4	us-gaap	Time Deposit Maturities Year Four TimeDepositMaturitiesYearFour	28639000	USD
CY2020Q4	us-gaap	Time Deposit Maturities Year Five TimeDepositMaturitiesYearFive	57847000	USD
CY2020Q4	us-gaap	Time Deposit Maturities After Year Five TimeDepositMaturitiesAfterYearFive	64000	USD
CY2020Q4	us-gaap	Time Deposits TimeDeposits	978779000	USD
CY2020Q4	gbci	Overdraft Demand Deposits Reclassified As Loans OverdraftDemandDepositsReclassifiedAsLoans	4713000	USD
CY2019Q4	gbci	Overdraft Demand Deposits Reclassified As Loans OverdraftDemandDepositsReclassifiedAsLoans	5514000	USD
CY2020Q4	us-gaap	Related Party Deposit Liabilities RelatedPartyDepositLiabilities	45179000	USD
CY2019Q4	us-gaap	Related Party Deposit Liabilities RelatedPartyDepositLiabilities	28972000	USD
CY2020Q4	us-gaap	Securities Sold Under Agreements To Repurchase Gross Including Not Subject To Master Netting Arrangement SecuritiesSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	1004583000	USD
CY2019Q4	us-gaap	Securities Sold Under Agreements To Repurchase Gross Including Not Subject To Master Netting Arrangement SecuritiesSoldUnderAgreementsToRepurchaseGrossIncludingNotSubjectToMasterNettingArrangement	569824000	USD
CY2020Q4	us-gaap	Pledged Financial Instruments Not Separately Reported Securities For Repurchase Agreements PledgedFinancialInstrumentsNotSeparatelyReportedSecuritiesForRepurchaseAgreements	1151264000	USD
CY2020	us-gaap	Gain Loss On Contract Termination GainLossOnContractTermination	-3531000	USD
CY2019Q4	us-gaap	Federal Home Loan Bank Advances Maturities Summary Due Within One Year Of Balance Sheet Date FederalHomeLoanBankAdvancesMaturitiesSummaryDueWithinOneYearOfBalanceSheetDate	31492000	USD
CY2019Q4	us-gaap	Federal Home Loan Bank Advances Maturities Summary Average Interest Rate Of Amounts Due Within One Year Of Balance Sheet Date FederalHomeLoanBankAdvancesMaturitiesSummaryAverageInterestRateOfAmountsDueWithinOneYearOfBalanceSheetDate	0.0181
CY2019Q4	us-gaap	Federal Home Loan Bank Advances Maturities Summary Due From One To Two Years Of Balance Sheet Date FederalHomeLoanBankAdvancesMaturitiesSummaryDueFromOneToTwoYearsOfBalanceSheetDate	5000000	USD
CY2019Q4	us-gaap	Federal Home Loan Bank Advances Maturities Summary Average Interest Rate One To Two Years From Balance Sheet Date FederalHomeLoanBankAdvancesMaturitiesSummaryAverageInterestRateOneToTwoYearsFromBalanceSheetDate	0.0295
CY2019Q4	us-gaap	Federal Home Loan Bank Advances Maturities Summary Due From Two To Three Years Of Balance Sheet Date FederalHomeLoanBankAdvancesMaturitiesSummaryDueFromTwoToThreeYearsOfBalanceSheetDate	889000	USD
CY2019Q4	us-gaap	Federal Home Loan Bank Advances Maturities Summary Average Interest Rate Two To Three Years From Balance Sheet Date FederalHomeLoanBankAdvancesMaturitiesSummaryAverageInterestRateTwoToThreeYearsFromBalanceSheetDate	0.0525
CY2019Q4	us-gaap	Federal Home Loan Bank Advances Maturities Summary Due From Three To Four Years Of Balance Sheet Date FederalHomeLoanBankAdvancesMaturitiesSummaryDueFromThreeToFourYearsOfBalanceSheetDate	165000	USD
CY2019Q4	us-gaap	Federal Home Loan Bank Advances Maturities Summary Average Interest Rate Three To Four Years From Balance Sheet Date FederalHomeLoanBankAdvancesMaturitiesSummaryAverageInterestRateThreeToFourYearsFromBalanceSheetDate	0.0545
CY2019Q4	us-gaap	Federal Home Loan Bank Advances Maturities Summary Due From Four To Five Years Of Balance Sheet Date FederalHomeLoanBankAdvancesMaturitiesSummaryDueFromFourToFiveYearsOfBalanceSheetDate	780000	USD
CY2020Q4	us-gaap	Line Of Credit Facility Maximum Borrowing Capacity LineOfCreditFacilityMaximumBorrowingCapacity	635000000	USD
CY2019Q4	us-gaap	Federal Home Loan Bank Advances Maturities Summary Average Interest Rate Four To Five Years From Balance Sheet Date FederalHomeLoanBankAdvancesMaturitiesSummaryAverageInterestRateFourToFiveYearsFromBalanceSheetDate	0.0431
CY2019Q4	us-gaap	Federal Home Loan Bank Advances Maturities Summary Due After Five Years Of Balance Sheet Date FederalHomeLoanBankAdvancesMaturitiesSummaryDueAfterFiveYearsOfBalanceSheetDate	285000	USD
CY2019Q4	us-gaap	Federal Home Loan Bank Advances Maturities Summary Average Interest Rate After Five Years From Balance Sheet Date FederalHomeLoanBankAdvancesMaturitiesSummaryAverageInterestRateAfterFiveYearsFromBalanceSheetDate	0.0631
CY2019Q4	us-gaap	Advances From Federal Home Loan Banks AdvancesFromFederalHomeLoanBanks	38611000	USD
CY2019Q4	gbci	Federal Home Loan Bank Advances Maturities Summary Average Interest Rate FederalHomeLoanBankAdvancesMaturitiesSummaryAverageInterestRate	0.0214
CY2020Q4	us-gaap	Subordinated Debt SubordinatedDebt	139959000	USD
CY2020	gbci	Maximum Number Of Consecutive Quarters For Deferral Of Interest Payments On Trust Preferred Securities MaximumNumberOfConsecutiveQuartersForDeferralOfInterestPaymentsOnTrustPreferredSecurities	20
CY2020Q4	gbci	Size Of Company Eligible For Tier1 Grandfather Provision SizeOfCompanyEligibleForTier1GrandfatherProvision	15000000000	USD
CY2020Q4	gbci	Size Of Company Eligible For Tier1 Grandfather Provision SizeOfCompanyEligibleForTier1GrandfatherProvision	15000000000	USD
CY2020Q4	gbci	Capital Conservation Buffer To Risk Weighted Assets Current Year CapitalConservationBufferToRiskWeightedAssetsCurrentYear	0.025
CY2020Q4	us-gaap	Capital Capital	1900621000	USD
CY2020Q4	us-gaap	Capital To Risk Weighted Assets CapitalToRiskWeightedAssets	0.1463
CY2020Q4	us-gaap	Capital Required For Capital Adequacy CapitalRequiredForCapitalAdequacy	1039094000	USD
CY2020Q4	us-gaap	Capital Required For Capital Adequacy To Risk Weighted Assets CapitalRequiredForCapitalAdequacyToRiskWeightedAssets	0.0800
CY2020Q4	us-gaap	Tier One Risk Based Capital TierOneRiskBasedCapital	1613066000	USD
CY2020Q4	us-gaap	Tier One Risk Based Capital To Risk Weighted Assets TierOneRiskBasedCapitalToRiskWeightedAssets	0.1242
CY2020Q4	us-gaap	Tier One Risk Based Capital Required For Capital Adequacy TierOneRiskBasedCapitalRequiredForCapitalAdequacy	779321000	USD
CY2020Q4	us-gaap	Tier One Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets	0.0600
CY2020Q4	us-gaap	Common Equity Tier One Capital CommonEquityTierOneCapital	1613066000	USD
CY2020Q4	us-gaap	Common Equity Tier One Capital Ratio CommonEquityTierOneCapitalRatio	0.1242
CY2020Q4	us-gaap	Common Equity Tier One Capital Required For Capital Adequacy CommonEquityTierOneCapitalRequiredForCapitalAdequacy	584491000	USD
CY2020Q4	gbci	Tier One Common Capital Required For Capital Adequacy To Risk Weighted Assets TierOneCommonCapitalRequiredForCapitalAdequacyToRiskWeightedAssets	0.0450
CY2020Q4	us-gaap	Tier One Leverage Capital TierOneLeverageCapital	1613066000	USD
CY2020Q4	us-gaap	Tier One Leverage Capital To Average Assets TierOneLeverageCapitalToAverageAssets	0.0912
CY2020Q4	us-gaap	Tier One Leverage Capital Required For Capital Adequacy TierOneLeverageCapitalRequiredForCapitalAdequacy	707823000	USD
CY2020Q4	us-gaap	Tier One Leverage Capital Required For Capital Adequacy To Average Assets TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets	0.0400
CY2019Q4	us-gaap	Capital Capital	1661249000	USD
CY2019Q4	us-gaap	Capital To Risk Weighted Assets CapitalToRiskWeightedAssets	0.1495
CY2019Q4	us-gaap	Capital Required For Capital Adequacy CapitalRequiredForCapitalAdequacy	888986000	USD
CY2019Q4	us-gaap	Capital Required For Capital Adequacy To Risk Weighted Assets CapitalRequiredForCapitalAdequacyToRiskWeightedAssets	0.0800
CY2019Q4	us-gaap	Tier One Risk Based Capital TierOneRiskBasedCapital	1528683000	USD
CY2019Q4	us-gaap	Tier One Risk Based Capital To Risk Weighted Assets TierOneRiskBasedCapitalToRiskWeightedAssets	0.1376
CY2019Q4	us-gaap	Tier One Risk Based Capital Required For Capital Adequacy TierOneRiskBasedCapitalRequiredForCapitalAdequacy	666740000	USD
CY2019Q4	us-gaap	Tier One Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets	0.0600
CY2019Q4	us-gaap	Common Equity Tier One Capital CommonEquityTierOneCapital	1398183000	USD
CY2019Q4	us-gaap	Common Equity Tier One Capital Ratio CommonEquityTierOneCapitalRatio	0.1258
CY2019Q4	us-gaap	Common Equity Tier One Capital Required For Capital Adequacy CommonEquityTierOneCapitalRequiredForCapitalAdequacy	500055000	USD
CY2019Q4	gbci	Tier One Common Capital Required For Capital Adequacy To Risk Weighted Assets TierOneCommonCapitalRequiredForCapitalAdequacyToRiskWeightedAssets	0.0450
CY2019Q4	us-gaap	Tier One Leverage Capital TierOneLeverageCapital	1528683000	USD
CY2019Q4	us-gaap	Tier One Leverage Capital To Average Assets TierOneLeverageCapitalToAverageAssets	0.1165
CY2019Q4	us-gaap	Tier One Leverage Capital Required For Capital Adequacy TierOneLeverageCapitalRequiredForCapitalAdequacy	524987000	USD
CY2019Q4	us-gaap	Tier One Leverage Capital Required For Capital Adequacy To Average Assets TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets	0.0400
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Available For Grant ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant	1929578	shares
CY2020	gbci	Consulting Fees ConsultingFees	11324000	USD
CY2019	gbci	Consulting Fees ConsultingFees	8276000	USD
CY2018	gbci	Consulting Fees ConsultingFees	7219000	USD
CY2020	us-gaap	Business Combination Integration Related Costs BusinessCombinationIntegrationRelatedCosts	7812000	USD
CY2019	us-gaap	Business Combination Integration Related Costs BusinessCombinationIntegrationRelatedCosts	8503000	USD
CY2018	us-gaap	Business Combination Integration Related Costs BusinessCombinationIntegrationRelatedCosts	6618000	USD
CY2020	gbci	Telephone Expenses TelephoneExpenses	5199000	USD
CY2019	gbci	Telephone Expenses TelephoneExpenses	4827000	USD
CY2018	gbci	Telephone Expenses TelephoneExpenses	4487000	USD
CY2020	gbci	Debit Card Expense DebitCardExpense	4947000	USD
CY2019	gbci	Debit Card Expense DebitCardExpense	5968000	USD
CY2018	gbci	Debit Card Expense DebitCardExpense	5104000	USD
CY2020	gbci	Deposit Related Expenses DepositRelatedExpenses	4944000	USD
CY2019	gbci	Deposit Related Expenses DepositRelatedExpenses	1757000	USD
CY2018	gbci	Deposit Related Expenses DepositRelatedExpenses	1234000	USD
CY2020	gbci	Loan Related Expenses LoanRelatedExpenses	4905000	USD
CY2019	gbci	Loan Related Expenses LoanRelatedExpenses	4140000	USD
CY2018	gbci	Loan Related Expenses LoanRelatedExpenses	3462000	USD
CY2020	gbci	Vie Write Downs Losses And Other Expenses VIEWriteDownsLossesAndOtherExpenses	4893000	USD
CY2019	gbci	Vie Write Downs Losses And Other Expenses VIEWriteDownsLossesAndOtherExpenses	4341000	USD
CY2018	gbci	Vie Write Downs Losses And Other Expenses VIEWriteDownsLossesAndOtherExpenses	3618000	USD
CY2020	us-gaap	Business Development BusinessDevelopment	4645000	USD
CY2019	us-gaap	Business Development BusinessDevelopment	4446000	USD
CY2018	us-gaap	Business Development BusinessDevelopment	4172000	USD
CY2020	us-gaap	Supplies Expense SuppliesExpense	3579000	USD
CY2019	us-gaap	Supplies Expense SuppliesExpense	3256000	USD
CY2018	us-gaap	Supplies Expense SuppliesExpense	3264000	USD
CY2020	us-gaap	Postage Expense PostageExpense	3347000	USD
CY2019	us-gaap	Postage Expense PostageExpense	3437000	USD
CY2018	us-gaap	Postage Expense PostageExpense	3104000	USD
CY2020	gbci	Miscellaneous Employee Expenses MiscellaneousEmployeeExpenses	2924000	USD
CY2019	gbci	Miscellaneous Employee Expenses MiscellaneousEmployeeExpenses	5138000	USD
CY2018	gbci	Miscellaneous Employee Expenses MiscellaneousEmployeeExpenses	4412000	USD
CY2020	gbci	Accounting Fees AccountingFees	1895000	USD
CY2019	gbci	Accounting Fees AccountingFees	1712000	USD
CY2018	gbci	Accounting Fees AccountingFees	1456000	USD
CY2020	us-gaap	Legal Fees LegalFees	1658000	USD
CY2019	us-gaap	Legal Fees LegalFees	1245000	USD
CY2018	us-gaap	Legal Fees LegalFees	1763000	USD
CY2018	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	11960000	USD
CY2020	us-gaap	Other Noninterest Expense OtherNoninterestExpense	66809000	USD
CY2020	us-gaap	Other Cost And Expense Operating OtherCostAndExpenseOperating	4737000	USD
CY2019	us-gaap	Other Cost And Expense Operating OtherCostAndExpenseOperating	5729000	USD
CY2018	us-gaap	Other Cost And Expense Operating OtherCostAndExpenseOperating	4381000	USD
CY2019	us-gaap	Other Noninterest Expense OtherNoninterestExpense	62775000	USD
CY2018	us-gaap	Other Noninterest Expense OtherNoninterestExpense	54294000	USD
CY2020	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	47775000	USD
CY2019	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	34461000	USD
CY2018	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	21510000	USD
CY2020	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	20728000	USD
CY2019	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	14545000	USD
CY2020	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	68503000	USD
CY2019	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	49006000	USD
CY2018	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	33470000	USD
CY2020	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-5396000	USD
CY2019	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-279000	USD
CY2018	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	5372000	USD
CY2020	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-1467000	USD
CY2019	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-77000	USD
CY2018	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	1489000	USD
CY2020	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-6863000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-356000	USD
CY2018	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	6861000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	61640000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	48650000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	40331000	USD
CY2020	us-gaap	Other Tax Expense Benefit OtherTaxExpenseBenefit	-315000	USD
CY2019	us-gaap	Other Tax Expense Benefit OtherTaxExpenseBenefit	-317000	USD
CY2018	us-gaap	Other Tax Expense Benefit OtherTaxExpenseBenefit	-443000	USD
CY2020	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.210
CY2019	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.210
CY2018	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.210
CY2020	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.046
CY2019	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.044
CY2018	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.048
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Tax Exempt Income EffectiveIncomeTaxRateReconciliationTaxExemptIncome	0.040
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Tax Exempt Income EffectiveIncomeTaxRateReconciliationTaxExemptIncome	0.037
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Tax Exempt Income EffectiveIncomeTaxRateReconciliationTaxExemptIncome	0.050
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Tax Credits EffectiveIncomeTaxRateReconciliationTaxCredits	0.042
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Tax Credits EffectiveIncomeTaxRateReconciliationTaxCredits	0.045
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Tax Credits EffectiveIncomeTaxRateReconciliationTaxCredits	0.042
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	0.014
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	0.016
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	0.016
CY2020	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.188
CY2019	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.188
CY2018	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.182
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Provision For Loan Losses DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsProvisionForLoanLosses	44040000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Provision For Loan Losses DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsProvisionForLoanLosses	31698000	USD
CY2020Q4	gbci	Deferred Tax Assets Operating Lease Liabilities DeferredTaxAssetsOperatingLeaseLiabilities	12551000	USD
CY2019Q4	gbci	Deferred Tax Assets Operating Lease Liabilities DeferredTaxAssetsOperatingLeaseLiabilities	11127000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Employee Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeBenefits	9309000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Employee Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeBenefits	6646000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Employee Compensation DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeCompensation	7638000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Employee Compensation DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeCompensation	7447000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Equity Method Investments DeferredTaxAssetsEquityMethodInvestments	4398000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Equity Method Investments DeferredTaxAssetsEquityMethodInvestments	5480000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	1884000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	2209000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	2262000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	3891000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	82082000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	68498000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Other Comprehensive Income DeferredTaxLiabilitiesOtherComprehensiveIncome	48505000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Other Comprehensive Income DeferredTaxLiabilitiesOtherComprehensiveIncome	13652000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets Intangible Assets DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsIntangibleAssets	14671000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets Intangible Assets DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsIntangibleAssets	16469000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	14654000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	13987000	USD
CY2020Q4	gbci	Deferred Tax Liabilities Operating Lease Rou Assets DeferredTaxLiabilitiesOperatingLeaseROUAssets	11830000	USD
CY2019Q4	gbci	Deferred Tax Liabilities Operating Lease Rou Assets DeferredTaxLiabilitiesOperatingLeaseROUAssets	10506000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Tax Deferred Income DeferredTaxLiabilitiesTaxDeferredIncome	8940000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Tax Deferred Income DeferredTaxLiabilitiesTaxDeferredIncome	7311000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Mortgage Servicing Rights DeferredTaxLiabilitiesMortgageServicingRights	2268000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Mortgage Servicing Rights DeferredTaxLiabilitiesMortgageServicingRights	411000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	5074000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	4125000	USD
CY2020Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	105942000	USD
CY2019Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	66461000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	23860000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	2037000	USD
CY2020Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	0	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	0	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued	0	USD
CY2020Q4	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued	0	USD
CY2019Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	0	USD
CY2020Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	0	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	266400000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	210544000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	181878000	USD
CY2020	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	94883864	shares
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	88255290	shares
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	83603515	shares
CY2020	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	48489	shares
CY2019	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	130485	shares
CY2018	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	73670	shares
CY2020	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	94932353	shares
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	88385775	shares
CY2018	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	83677185	shares
CY2020	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.81
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.39
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.18
CY2020	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.81
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.38
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.17
CY2020	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	88240	shares
CY2019	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	0	shares
CY2018	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	1357	shares
CY2020Q1	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	142865000	USD
CY2020Q2	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	155404000	USD
CY2020Q3	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	157487000	USD
CY2020Q4	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	171308000	USD
CY2020Q4	us-gaap	Interest Expense InterestExpense	5550000	USD
CY2020Q1	us-gaap	Interest Expense InterestExpense	8496000	USD
CY2020Q2	us-gaap	Interest Expense InterestExpense	7185000	USD
CY2020Q3	us-gaap	Interest Expense InterestExpense	6084000	USD
CY2020Q1	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	134369000	USD
CY2020Q2	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	148219000	USD
CY2020Q3	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	151403000	USD
CY2020Q4	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	165758000	USD
CY2020Q1	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	19185000	USD
CY2020Q2	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	16929000	USD
CY2020Q3	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	5186000	USD
CY2020Q4	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	-1535000	USD
CY2020Q1	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	115184000	USD
CY2020Q2	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	131290000	USD
CY2020Q3	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	146217000	USD
CY2020Q4	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	167293000	USD
CY2020Q1	us-gaap	Noninterest Income NoninterestIncome	33272000	USD
CY2020Q2	us-gaap	Noninterest Income NoninterestIncome	41224000	USD
CY2020Q3	us-gaap	Noninterest Income NoninterestIncome	53667000	USD
CY2020Q4	us-gaap	Noninterest Income NoninterestIncome	44704000	USD
CY2020Q1	us-gaap	Noninterest Expense NoninterestExpense	95487000	USD
CY2020Q2	us-gaap	Noninterest Expense NoninterestExpense	94764000	USD
CY2020Q3	us-gaap	Noninterest Expense NoninterestExpense	103373000	USD
CY2020Q4	us-gaap	Noninterest Expense NoninterestExpense	111187000	USD
CY2020Q1	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	52969000	USD
CY2020Q2	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	77750000	USD
CY2020Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	96511000	USD
CY2020Q4	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	100810000	USD
CY2020Q1	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	9630000	USD
CY2020Q2	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	14306000	USD
CY2020Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	18754000	USD
CY2020Q4	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	18950000	USD
CY2020Q1	us-gaap	Net Income Loss NetIncomeLoss	43339000	USD
CY2020Q2	us-gaap	Net Income Loss NetIncomeLoss	63444000	USD
CY2020Q3	us-gaap	Net Income Loss NetIncomeLoss	77757000	USD
CY2020Q4	us-gaap	Net Income Loss NetIncomeLoss	81860000	USD
CY2020Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.46
CY2020Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.67
CY2020Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.81
CY2020Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.86
CY2020Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.46
CY2020Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.66
CY2020Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.81
CY2020Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.86
CY2019Q1	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	126116000	USD
CY2019Q2	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	132385000	USD
CY2019Q3	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	142395000	USD
CY2019Q4	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	145281000	USD
CY2019Q1	us-gaap	Interest Expense InterestExpense	10904000	USD
CY2019Q2	us-gaap	Interest Expense InterestExpense	12089000	USD
CY2019Q3	us-gaap	Interest Expense InterestExpense	10947000	USD
CY2019Q4	us-gaap	Interest Expense InterestExpense	8833000	USD
CY2019Q1	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	115212000	USD
CY2019Q2	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	120296000	USD
CY2019Q3	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	131448000	USD
CY2019Q4	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	136448000	USD
CY2019Q1	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	57000	USD
CY2019Q2	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	0	USD
CY2019Q3	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	0	USD
CY2019Q4	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	0	USD
CY2019Q1	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	115155000	USD
CY2019Q2	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	120296000	USD
CY2019Q3	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	131448000	USD
CY2019Q4	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	136448000	USD
CY2019Q1	us-gaap	Noninterest Income NoninterestIncome	28474000	USD
CY2019Q2	us-gaap	Noninterest Income NoninterestIncome	30834000	USD
CY2019Q3	us-gaap	Noninterest Income NoninterestIncome	43049000	USD
CY2019Q4	us-gaap	Noninterest Income NoninterestIncome	28417000	USD
CY2019Q1	us-gaap	Noninterest Expense NoninterestExpense	82830000	USD
CY2019Q2	us-gaap	Noninterest Expense NoninterestExpense	86170000	USD
CY2019Q3	us-gaap	Noninterest Expense NoninterestExpense	110675000	USD
CY2019Q4	us-gaap	Noninterest Expense NoninterestExpense	95252000	USD
CY2019Q1	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	60799000	USD
CY2019Q2	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	64960000	USD
CY2019Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	63822000	USD
CY2019Q4	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	69613000	USD
CY2019Q1	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	11667000	USD
CY2019Q2	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	12568000	USD
CY2019Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	12212000	USD
CY2019Q4	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	12203000	USD
CY2019Q1	us-gaap	Net Income Loss NetIncomeLoss	49132000	USD
CY2019Q2	us-gaap	Net Income Loss NetIncomeLoss	52392000	USD
CY2019Q3	us-gaap	Net Income Loss NetIncomeLoss	51610000	USD
CY2019Q4	us-gaap	Net Income Loss NetIncomeLoss	57410000	USD
CY2019Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.58
CY2019Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.61
CY2019Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.57
CY2019Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.62
CY2019Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.58
CY2019Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.61
CY2019Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.57
CY2019Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.62
CY2019	gbci	Fair Value Measurement Transfers From One Level To Another FairValueMeasurementTransfersFromOneLevelToAnother	0	USD
CY2020	gbci	Fair Value Measurement Transfers From One Level To Another FairValueMeasurementTransfersFromOneLevelToAnother	0	USD
CY2018	gbci	Fair Value Measurement Transfers From One Level To Another FairValueMeasurementTransfersFromOneLevelToAnother	0	USD
CY2020Q4	us-gaap	Other Commitment OtherCommitment	3022620000	USD
CY2019Q4	us-gaap	Other Commitment OtherCommitment	2482673000	USD

Files In Submission

Name	View Source	Status
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$GBCI
GLACIER BANCORP, INC. Stock $gbci

2020 Q4 Form 10-K Financial Statement

#000086867121000037 Filed on March 01, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$GBCI GLACIER BANCORP, INC. Stock $gbci

2020 Q4 Form 10-K Financial Statement

#000086867121000037 Filed on March 01, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$GBCI
GLACIER BANCORP, INC. Stock $gbci