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Provision for unfunded commitments.

No definition available.

Name:	ibkc_ProvisionForUnfundedCommitments
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Data Type:	xbrli:monetaryItemType
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Period Type:	duration

provision for unfunded commitment, acquired

No definition available.

Name:	ibkc_Provisionforunfundedcommitmentacquired
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Reserve for unfunded commitments.

No definition available.

Name:	ibkc_ReserveForUnfundedCommitments
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Reserve For Unfunded Commitments

No definition available.

Name:	ibkc_ReserveForUnfundedCommitmentsRollForward
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Data Type:	xbrli:stringItemType
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Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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A valuation allowance for financing receivables that are expected to be uncollectible.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Period Type:	instant

Amount of expense related to estimated loss from loan and lease transactions.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-SubTopic 225
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