XML 120 R106.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Consideration Transferred, Identifiable Net Assets Acquired and Goodwill Recognized (Details) (USD $) In Thousands, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Liabilities assumed |  |  |
Bargain purchase gain | $ (680)us-gaap_BusinessCombinationBargainPurchaseGainRecognizedAmount | $ 0us-gaap_BusinessCombinationBargainPurchaseGainRecognizedAmount | $ 0us-gaap_BusinessCombinationBargainPurchaseGainRecognizedAmount
Goodwill recognized | 0us-gaap_GoodwillAcquiredDuringPeriod | 23,606us-gaap_GoodwillAcquiredDuringPeriod | 0us-gaap_GoodwillAcquiredDuringPeriod
FNBR Holding Corporation |  |  |
Fair value of consideration transferred |  |  |
Fair value of Company shares issued, net of equity issuance costs | 15,127us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable / us-gaap_BusinessAcquisitionAxis = gbci_FNBRHoldingCorporationMember |  |
Cash consideration for outstanding shares | 16,690us-gaap_PaymentsToAcquireBusinessesGross / us-gaap_BusinessAcquisitionAxis = gbci_FNBRHoldingCorporationMember |  |
Contingent consideration | 0gbci_BusinessCombinationContingentConsideration / us-gaap_BusinessAcquisitionAxis = gbci_FNBRHoldingCorporationMember |  |
Total fair value of consideration transferred | 31,817us-gaap_BusinessCombinationConsiderationTransferred1 / us-gaap_BusinessAcquisitionAxis = gbci_FNBRHoldingCorporationMember |  |
Identifiable assets acquired |  |  |
Cash and cash equivalents | 14,578us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents / us-gaap_BusinessAcquisitionAxis = gbci_FNBRHoldingCorporationMember |  |
Investment securities | 157,018gbci_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedMarketableSecurities / us-gaap_BusinessAcquisitionAxis = gbci_FNBRHoldingCorporationMember |  |
Loans receivable | 137,488gbci_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedLoansReceivable / us-gaap_BusinessAcquisitionAxis = gbci_FNBRHoldingCorporationMember |  |
Core deposit intangible | 4,199us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles / us-gaap_BusinessAcquisitionAxis = gbci_FNBRHoldingCorporationMember |  |
Accrued income and other assets | 35,884gbci_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedOtherAssets / us-gaap_BusinessAcquisitionAxis = gbci_FNBRHoldingCorporationMember |  |
Total identifiable assets acquired | 349,167us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets / us-gaap_BusinessAcquisitionAxis = gbci_FNBRHoldingCorporationMember |  |
Liabilities assumed |  |  |
Deposits | 309,641gbci_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedDeposits / us-gaap_BusinessAcquisitionAxis = gbci_FNBRHoldingCorporationMember |  |
Federal Home Loan Bank advances | 0gbci_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedFederalHomeLoanBankAdvances / us-gaap_BusinessAcquisitionAxis = gbci_FNBRHoldingCorporationMember |  |
Accrued expenses and other liabilities | 7,029gbci_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedOtherLiabilities / us-gaap_BusinessAcquisitionAxis = gbci_FNBRHoldingCorporationMember |  |
Total liabilities assumed | 316,670us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities / us-gaap_BusinessAcquisitionAxis = gbci_FNBRHoldingCorporationMember |  |
Total identifiable net assets | 32,497us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet / us-gaap_BusinessAcquisitionAxis = gbci_FNBRHoldingCorporationMember |  |
Bargain purchase gain | (680)us-gaap_BusinessCombinationBargainPurchaseGainRecognizedAmount / us-gaap_BusinessAcquisitionAxis = gbci_FNBRHoldingCorporationMember |  |
North Cascades Bancshares |  |  |
Fair value of consideration transferred |  |  |
Fair value of Company shares issued, net of equity issuance costs |  | 16,743us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable / us-gaap_BusinessAcquisitionAxis = gbci_NorthCascadesBancsharesMember |
Cash consideration for outstanding shares |  | 13,833us-gaap_PaymentsToAcquireBusinessesGross / us-gaap_BusinessAcquisitionAxis = gbci_NorthCascadesBancsharesMember |
Contingent consideration |  | 0gbci_BusinessCombinationContingentConsideration / us-gaap_BusinessAcquisitionAxis = gbci_NorthCascadesBancsharesMember |
Total fair value of consideration transferred |  | 30,576us-gaap_BusinessCombinationConsiderationTransferred1 / us-gaap_BusinessAcquisitionAxis = gbci_NorthCascadesBancsharesMember |
Identifiable assets acquired |  |  |
Cash and cash equivalents |  | 27,865us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents / us-gaap_BusinessAcquisitionAxis = gbci_NorthCascadesBancsharesMember |
Investment securities |  | 48,058gbci_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedMarketableSecurities / us-gaap_BusinessAcquisitionAxis = gbci_NorthCascadesBancsharesMember |
Loans receivable |  | 215,986gbci_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedLoansReceivable / us-gaap_BusinessAcquisitionAxis = gbci_NorthCascadesBancsharesMember |
Core deposit intangible |  | 3,660us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles / us-gaap_BusinessAcquisitionAxis = gbci_NorthCascadesBancsharesMember |
Accrued income and other assets |  | 24,262gbci_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedOtherAssets / us-gaap_BusinessAcquisitionAxis = gbci_NorthCascadesBancsharesMember |
Total identifiable assets acquired |  | 319,831us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets / us-gaap_BusinessAcquisitionAxis = gbci_NorthCascadesBancsharesMember |
Liabilities assumed |  |  |
Deposits |  | 294,980gbci_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedDeposits / us-gaap_BusinessAcquisitionAxis = gbci_NorthCascadesBancsharesMember |
Federal Home Loan Bank advances |  | 0gbci_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedFederalHomeLoanBankAdvances / us-gaap_BusinessAcquisitionAxis = gbci_NorthCascadesBancsharesMember |
Accrued expenses and other liabilities |  | 4,472gbci_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedOtherLiabilities / us-gaap_BusinessAcquisitionAxis = gbci_NorthCascadesBancsharesMember |
Total liabilities assumed |  | 299,452us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities / us-gaap_BusinessAcquisitionAxis = gbci_NorthCascadesBancsharesMember |
Total identifiable net assets |  | 20,379us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet / us-gaap_BusinessAcquisitionAxis = gbci_NorthCascadesBancsharesMember |
Goodwill recognized |  | 10,197us-gaap_GoodwillAcquiredDuringPeriod / us-gaap_BusinessAcquisitionAxis = gbci_NorthCascadesBancsharesMember |
Wheatland Bankshares |  |  |
Fair value of consideration transferred |  |  |
Fair value of Company shares issued, net of equity issuance costs |  | 28,290us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable / us-gaap_BusinessAcquisitionAxis = gbci_WheatlandBanksharesMember |
Cash consideration for outstanding shares |  | 11,025us-gaap_PaymentsToAcquireBusinessesGross / us-gaap_BusinessAcquisitionAxis = gbci_WheatlandBanksharesMember |
Contingent consideration |  | 0gbci_BusinessCombinationContingentConsideration / us-gaap_BusinessAcquisitionAxis = gbci_WheatlandBanksharesMember |
Total fair value of consideration transferred |  | 39,315us-gaap_BusinessCombinationConsiderationTransferred1 / us-gaap_BusinessAcquisitionAxis = gbci_WheatlandBanksharesMember |
Identifiable assets acquired |  |  |
Cash and cash equivalents |  | 23,148us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents / us-gaap_BusinessAcquisitionAxis = gbci_WheatlandBanksharesMember |
Investment securities |  | 75,643gbci_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedMarketableSecurities / us-gaap_BusinessAcquisitionAxis = gbci_WheatlandBanksharesMember |
Loans receivable |  | 171,199gbci_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedLoansReceivable / us-gaap_BusinessAcquisitionAxis = gbci_WheatlandBanksharesMember |
Core deposit intangible |  | 2,079us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles / us-gaap_BusinessAcquisitionAxis = gbci_WheatlandBanksharesMember |
Accrued income and other assets |  | 15,063gbci_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedOtherAssets / us-gaap_BusinessAcquisitionAxis = gbci_WheatlandBanksharesMember |
Total identifiable assets acquired |  | 287,132us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets / us-gaap_BusinessAcquisitionAxis = gbci_WheatlandBanksharesMember |
Liabilities assumed |  |  |
Deposits |  | 255,197gbci_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedDeposits / us-gaap_BusinessAcquisitionAxis = gbci_WheatlandBanksharesMember |
Federal Home Loan Bank advances |  | 5,467gbci_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedFederalHomeLoanBankAdvances / us-gaap_BusinessAcquisitionAxis = gbci_WheatlandBanksharesMember |
Accrued expenses and other liabilities |  | 562gbci_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedOtherLiabilities / us-gaap_BusinessAcquisitionAxis = gbci_WheatlandBanksharesMember |
Total liabilities assumed |  | 261,226us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities / us-gaap_BusinessAcquisitionAxis = gbci_WheatlandBanksharesMember |
Total identifiable net assets |  | 25,906us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet / us-gaap_BusinessAcquisitionAxis = gbci_WheatlandBanksharesMember |
Goodwill recognized |  | $ 13,409us-gaap_GoodwillAcquiredDuringPeriod / us-gaap_BusinessAcquisitionAxis = gbci_WheatlandBanksharesMember |

X
- Definition Contingent Consideration due on business combination. + References No definition available. + Details
Name: | gbci_BusinessCombinationContingentConsideration
Namespace Prefix: | gbci_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of deposits assumed at the acquisition date + References No definition available. + Details
Name: | gbci_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedDeposits
Namespace Prefix: | gbci_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Federal Home Loan Bank Advances + References No definition available. + Details
Name: | gbci_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedFederalHomeLoanBankAdvances
Namespace Prefix: | gbci_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Loans Receivable + References No definition available. + Details
Name: | gbci_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedLoansReceivable
Namespace Prefix: | gbci_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of investments in debt and equity securities, including, but not limited to, held-to-maturity, trading and available-for-sale acquired at the acquisition date. + References No definition available. + Details
Name: | gbci_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedMarketableSecurities
Namespace Prefix: | gbci_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of other assets acquired at the acquisition date. + References No definition available. + Details
Name: | gbci_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedOtherAssets
Namespace Prefix: | gbci_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Liabilities + References No definition available. + Details
Name: | gbci_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedOtherLiabilities
Namespace Prefix: | gbci_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition In a business combination in which the amount of net identifiable assets acquired and liabilities assumed exceeds the aggregate consideration transferred or to be transferred (as defined), this element represents the amount of gain recognized by the entity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (f)(1) -URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 30 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6571-128477 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 30 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6527-128477 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 25 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6396-128476 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 25 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6387-128476 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 25 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6393-128476 + Details
Name: | us-gaap_BusinessCombinationBargainPurchaseGainRecognizedAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 30 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6578-128477 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 30 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6613-128477 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479 + Details
Name: | us-gaap_BusinessCombinationConsiderationTransferred1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_BusinessCombinationConsiderationTransferredAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of equity interests of the acquirer, including instruments or interests issued or issuable in consideration for the business combination. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 30 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6578-128477 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 30 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6613-128477 + Details
Name: | us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of assets acquired at the acquisition date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=39739317&loc=d3e4845-128472 + Details
Name: | us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of currency on hand as well as demand deposits with banks or financial institutions, acquired at the acquisition date. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=39739317&loc=d3e4845-128472 + Details
Name: | us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The amount of identifiable intangible assets recognized as of the acquisition date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=39739317&loc=d3e4845-128472 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 55 -Paragraph 37 -URI http://asc.fasb.org/extlink&oid=35744172&loc=d3e2207-128464 + Details
Name: | us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of liabilities assumed at the acquisition date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=39739317&loc=d3e4845-128472 + Details
Name: | us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount recognized as of the acquisition date for the identifiable assets acquired in excess of (less than) the aggregate liabilities assumed. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=39739317&loc=d3e4845-128472 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 55 -Paragraph 37 -URI http://asc.fasb.org/extlink&oid=35744172&loc=d3e2207-128464 + Details
Name: | us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267 + Details
Name: | us-gaap_GoodwillAcquiredDuringPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585 + Details
Name: | us-gaap_PaymentsToAcquireBusinessesGross
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=gbci_FNBRHoldingCorporationMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=gbci_NorthCascadesBancsharesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=gbci_WheatlandBanksharesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |