XML 72 R56.htm IDEA: XBRL DOCUMENT
v3.22.0.1

Nature of Operations and Summary of Significant Accounting Policies - Narrative (Details) | 12 Months Ended
--- | ---
Dec. 31, 2021 USD ($) operatingSegment bankDivision reporting_unit quarter component | Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($)
Property, Plant and Equipment |  |  |
Number of bank divisions | bankDivision | 17 |  |
Number of operating segments | operatingSegment | 1 |  |
Maximum period of original maturity to be included in cash and cash equivalents | 3 months |  |
Federal reserve balance or cash on hand required | $ 0 |  |
Minimum period past due to consider loans as delinquent | 30 days |  |
Minimum period past due to consider loans as non accrual | 90 days |  |
Financing receivable, allowance for credit losses, forecasting period | quarter | 4 |  |
Financing receivable, allowance for credit losses, number of components | component | 2 |  |
Provision for credit losses on debt securities | $ 0 | $ 0 | $ 0
Maximum term leases will be considered short-term | 12 months |  |
Maximum period up to which purchase price of business is allocated to assets acquired and liabilities assumed | 1 year |  |
Number of reporting units subsequent to aggregation for goodwill assessment | reporting_unit | 1 |  |
Revenue from contracts with customers | $ 65,194,000 | 54,520,000 | $ 69,877,000
Impairment losses on receivables related to contracts with customers | $ 0 | $ 0 |
Percentage of likelihood for term more likely than not as it relates to income taxes | 50.00% |  |
Minimum Range |  |  |
Property, Plant and Equipment |  |  |
Period past due to consider loan as purchased credit-deteriorated loan | 90 days |  |
Minimum number of days delinquent to charge off loans | 120 days |  |
Number of years for home equity loan origination term | 10 years |  |
Period past due to consider loans as delinquent | 30 days |  |
Period past due to consider loans as non accrual | 90 days |  |
Minimum Range | Office Buildings |  |  |
Property, Plant and Equipment |  |  |
Useful life of premises and equipment | 15 years |  |
Minimum Range | Furniture, Fixtures and Equipment |  |  |
Property, Plant and Equipment |  |  |
Useful life of premises and equipment | 3 years |  |
Maximum Range |  |  |
Property, Plant and Equipment |  |  |
Number of years for home equity loan origination term | 15 years |  |
Period past due to consider loans as delinquent | 89 days |  |
Maximum Range | Office Buildings |  |  |
Property, Plant and Equipment |  |  |
Useful life of premises and equipment | 40 years |  |
Maximum Range | Furniture, Fixtures and Equipment |  |  |
Property, Plant and Equipment |  |  |
Useful life of premises and equipment | 10 years |  |

X
- Definition Federal Reserve balance or cash on hand required. + References No definition available. + Details
Name: | gbci_FederalReserveBalanceOrCashOnHandRequired
Namespace Prefix: | gbci_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Financing Receivable, Allowance for Credit Losses, Forecasting Period + References No definition available. + Details
Name: | gbci_FinancingReceivableAllowanceForCreditLossesForecastingPeriod
Namespace Prefix: | gbci_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Financing Receivable, Allowance for Credit Losses, Number of Components + References No definition available. + Details
Name: | gbci_FinancingReceivableAllowanceForCreditLossesNumberOfComponents
Namespace Prefix: | gbci_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Threshold period for when financing receivable is considered past due to write off as uncollectible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | gbci_FinancingReceivableThresholdPeriodPastDueWriteoff1
Namespace Prefix: | gbci_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Maximum Period Of Original Maturity To Be Included In Cash And Cash Equivalents + References No definition available. + Details
Name: | gbci_MaximumPeriodOfOriginalMaturityToBeIncludedInCashAndCashEquivalents
Namespace Prefix: | gbci_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Maximum Period up to Which Purchase Price of Business is Allocated to Assets Acquired and Liabilities Assumed. + References No definition available. + Details
Name: | gbci_MaximumPeriodUpToWhichPurchasePriceOfBusinessIsAllocatedToAssetsAcquiredAndLiabilitiesAssumed
Namespace Prefix: | gbci_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Maximum Term Leases Will Be Considered Short-term + References No definition available. + Details
Name: | gbci_MaximumTermLeasesWillBeConsideredShortTerm
Namespace Prefix: | gbci_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Minimum Period Past Due To Consider Loans As Delinquent + References No definition available. + Details
Name: | gbci_MinimumPeriodPastDueToConsiderLoansAsDelinquent
Namespace Prefix: | gbci_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Minimum Period Past Due To Consider Loans As Non Accrual + References No definition available. + Details
Name: | gbci_MinimumPeriodPastDueToConsiderLoansAsNonAccrual
Namespace Prefix: | gbci_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of Bank Divisions + References No definition available. + Details
Name: | gbci_NumberOfBankDivisions
Namespace Prefix: | gbci_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of Reporting Units Subsequent to Aggregation for Goodwill Assessment + References No definition available. + Details
Name: | gbci_NumberOfReportingUnitsSubsequentToAggregationForGoodwillAssessment
Namespace Prefix: | gbci_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number Of Years For Home Equity Loan Origination Term + References No definition available. + Details
Name: | gbci_NumberOfYearsForHomeEquityLoanOriginationTerm
Namespace Prefix: | gbci_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of likelihood for term more likely than not. + References No definition available. + Details
Name: | gbci_PercentageOfLikelihoodForTermMoreLikelyThanNot
Namespace Prefix: | gbci_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Period Past Due to Consider Loan As Purchased Credit-Deteriorated Loan + References No definition available. + Details
Name: | gbci_PeriodPastDueToConsiderLoanAsPurchasedCreditDeterioratedLoan
Namespace Prefix: | gbci_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Period Past Due to Consider Loans as Delinquent + References No definition available. + Details
Name: | gbci_PeriodPastDueToConsiderLoansAsDelinquent
Namespace Prefix: | gbci_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Period Past Due to Consider Loans as Non Accrual + References No definition available. + Details
Name: | gbci_PeriodPastDueToConsiderLoansAsNonAccrual
Namespace Prefix: | gbci_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of accumulated impairment loss for asset recognized from cost incurred to obtain or fulfill contract with customer. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 340 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123353750&loc=SL49131252-203054 + Details
Name: | us-gaap_CapitalizedContractCostAccumulatedImpairment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of expense (reversal of expense) for expected credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), from change in present value of expected cash flows. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=124258926&loc=SL82922868-210454 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=124269663&loc=SL82922897-210455 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleChangeInPresentValueExpenseReversal
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 18 -URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8672-108599 + Details
Name: | us-gaap_NumberOfOperatingSegments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_PropertyPlantAndEquipmentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment. + References No definition available. + Details
Name: | us-gaap_PropertyPlantAndEquipmentUsefulLife
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 41 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e9038-108599 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130545-203045 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 32 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 32 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 30 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8906-108599 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 22 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8736-108599 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 22 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8736-108599 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130543-203045 Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 42 -URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e9054-108599 Reference 10: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 40 -URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e9031-108599 Reference 11: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 924 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 11.L) -URI http://asc.fasb.org/extlink&oid=6472922&loc=d3e499488-122856 + Details
Name: | us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_BuildingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_FurnitureAndFixturesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |