Long-Term Debt (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015
Debt Instrument
Long-term debt	$ 628,953	$ 340,447
IBERIABANK
Debt Instrument
Long-term debt	$ 508,843	220,337
IBERIABANK \| Federal Home Loan Bank Notes
Debt Instrument
Minimum FHLB advance amortization period	1 year 6 months
Maximum FHLB advance amortization period	30 years
Long-term debt	$ 480,118	136,628
IBERIABANK \| Federal Home Loan Bank Notes \| Blanket Floating Lien
Debt Instrument
Additional advances available from FHLB	4,900,000
IBERIABANK \| Federal Home Loan Bank Notes \| Pledge of Investment Securities
Debt Instrument
Additional advances available from FHLB	1,500,000
IBERIABANK Corporation \| Junior Subordinated Debt
Debt Instrument
Long-term debt	$ 120,110	$ 120,110
Debt Instrument term	30 years
Earliest call date after issue	5 years
Earliest interest payment deferral date (in years or 20 consecutive quarters)	5 years
Percent of subordinate debt excluded from Tier 1 regulatory capital requirements	100.00%	75.00%
Increase in percent of subordinate debt excluded from Tier 1 regulatory capital requirements	25.00%
Weighted Average \| IBERIABANK \| Federal Home Loan Bank Notes
Debt Instrument
Weighted average advance rate on FHLB advances	1.76%	3.79%

Period of time between issuance and earliest call date of debt instrument.

No definition available.

Name:	ibkc_DebtInstrumentCallTermEarliest
Namespace Prefix:	ibkc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument, Interest Payment Deferral Term, Earliest

+ References

No definition available.

+ Details

Name:	ibkc_DebtInstrumentInterestPaymentDeferralTermEarliest
Namespace Prefix:	ibkc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The minimum amortization period for Federal Home Loan Bank advances.

+ References

No definition available.

+ Details

Name:	ibkc_FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresDudDateEarliestMinimum
Namespace Prefix:	ibkc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The maximum amortization period for Federal Home Loan Bank advances.

+ References

No definition available.

+ Details

Name:	ibkc_FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresDueDateLastMaximum
Namespace Prefix:	ibkc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Long-Term Debt, Excluded From Tier 1 Regulatory Capital Requirements, Increase in Percentage

+ References

No definition available.

+ Details

Name:	ibkc_LongTermDebtExcludedFromTier1RegulatoryCapitalRequirementsIncreaseinPercentage
Namespace Prefix:	ibkc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Long-Term Debt, Excluded From Tier 1 Regulatory Capital Requirements, Percentage

+ References

No definition available.

+ Details

Name:	ibkc_LongTermDebtExcludedFromTier1RegulatoryCapitalRequirementsPercentage
Namespace Prefix:	ibkc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- 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_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of advances or credit lines available from the Federal Home Loan Bank (FHLB).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.13(3)(a))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22 (b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6479118&loc=d3e64650-112822

+ Details

Name:	us-gaap_FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresAmountOfAvailableUnusedFunds
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

States the interest rate applicable to Federal Home Loan Bank advances outstanding as of the Balance Sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6479118&loc=d3e64650-112822

+ Details

Name:	us-gaap_FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresInterestRateAtPeriodEnd
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	dei_LegalEntityAxis=us-gaap_SubsidiariesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_FederalHomeLoanBankAdvancesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=ibkc_BlanketFloatingLienMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=ibkc_PledgeOfInvestmentSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=us-gaap_ParentCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_JuniorSubordinatedDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_WeightedAverageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: