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Deposits - Narrative (Details) - USD ($) | Dec. 31, 2021 | Dec. 31, 2020
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Deposits |  |
FDIC Insurance limit | $ 250,000 |
Time deposits that meet or exceed FDIC Insurance limit | 298,512,000 | $ 297,975,000
Overdraft demand deposits reclassified as loans | 10,036,000 | 4,713,000
Deposits with related parties | $ 55,966,000 | $ 45,179,000

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- Definition Deposits textual. + References No definition available. + Details
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Balance Type: | na
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- Definition Overdraft demand deposits reclassified as loans. + References No definition available. + Details
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Namespace Prefix: | gbci_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
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- Definition The aggregate amount of domestic time deposit liabilities (including certificates of deposits, individual retirement accounts and open accounts) in denominations that meet or exceed the FDIC Insurance limit. + References No definition available. + Details
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Namespace Prefix: | gbci_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
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- Definition The amount of cash deposited in financial institutions as of the balance sheet date that is insured by the Federal Deposit Insurance Corporation. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Amount of deposits held by the entity for a related party (entity, shareholder, employee). + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08(k)(1)) -URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690 + Details
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