Represents the estimated fair value of letters of credit outstanding at the balance sheet date.

No definition available.

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Namespace Prefix:	ibkc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

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- 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

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Period Type:	duration

- Definition

The value (monetary amount) of the award the plaintiff seeks in the legal matter.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 9
-Subparagraph (a)
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118942415&loc=d3e14326-108349

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Balance Type:	debit
Period Type:	duration

- Definition

The amount of loss pertaining to the specified contingency that was charged against earnings in the period, including the effects of revisions in previously reported estimates.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118942415&loc=d3e14326-108349

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- Details

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Namespace Prefix:
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- Details

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Commitments and Contingencies (Detail) - USD ($) $ in Millions		9 Months Ended
	Dec. 11, 2017	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Fair value of guarantees under commercial and standby letters of credit			$ 3.3	$ 2.4
Settled Litigation
Loss Contingencies [Line Items]
Settlement amount	$ 11.7
Pending Litigation
Loss Contingencies [Line Items]
Damages sought		$ 11.7