Acquisition and Disposition Activity - Schedule of Business Acquisitions, by Acquisition (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014
Trust One- Memphis [Member] \| As Acquired [Member]
Business Acquisition [Line Items]
Cash and cash equivalents	$ 92,060
Loans	88,179
Other real estate owned	1,325
Other assets	368
Total Assets	181,932
Interest-bearing deposits	164,942
Non-interest-bearing deposits	26,373
Deferred tax liability	0
Other liabilities	84
Total Liabilities	191,399
Trust One- Memphis [Member] \| Preliminary Fair Value Adjustments [Member]
Business Acquisition [Line Items]
Total Assets	871
Deferred tax liability	0
Trust One- Memphis [Member] \| As Recorded by IBERIABANK [Member]
Business Acquisition [Line Items]
Cash and cash equivalents	92,060
Loans	86,453
Other real estate owned	1,325
Core deposit intangible	2,597
Other assets	368
Total Assets	182,803
Interest-bearing deposits	164,942
Non-interest-bearing deposits	26,373
Deferred tax liability	0
Other liabilities	84
Total Liabilities	191,399
Teche [Member] \| As Acquired [Member]
Business Acquisition [Line Items]
Cash and cash equivalents	71,611
Investment securities	24,077
Loans	716,327
Other real estate owned	329
Deferred tax asset	1,057
Other assets	56,730
Total Assets	870,131
Interest-bearing deposits	520,446
Non-interest-bearing deposits	118,256
Borrowings	134,228
Other liabilities	5,376
Total Liabilities	778,306
Teche [Member] \| Preliminary Fair Value Adjustments [Member]
Business Acquisition [Line Items]
Investment securities	1,092
Loans	(15,869)
Other real estate owned	(153)
Core deposit intangible	7,440
Deferred tax asset	4,835
Other assets	(5,653)
Total Assets	(8,308)
Interest-bearing deposits	902
Borrowings	6,304
Total Liabilities	7,206
Teche [Member] \| As Recorded by IBERIABANK [Member]
Business Acquisition [Line Items]
Cash and cash equivalents	71,611
Investment securities	25,169
Loans	700,458
Other real estate owned	176
Core deposit intangible	7,440
Deferred tax asset	5,892
Other assets	51,077
Total Assets	861,823
Interest-bearing deposits	521,348
Non-interest-bearing deposits	118,256
Borrowings	140,532
Other liabilities	5,376
Total Liabilities	785,512
First Private [Member] \| As Acquired [Member]
Business Acquisition [Line Items]
Cash and cash equivalents	26,621
Investment securities	18,920
Loans	300,177
Deferred tax asset	530
Other assets	5,148
Total Assets	351,396
Interest-bearing deposits	261,713
Non-interest-bearing deposits	50,334
Borrowings	6,451
Other liabilities	306
Total Liabilities	318,804
First Private [Member] \| Preliminary Fair Value Adjustments [Member]
Business Acquisition [Line Items]
Investment securities	297
Loans	(910)
Core deposit intangible	506
Deferred tax asset	122
Total Assets	15
Interest-bearing deposits	220
Total Liabilities	220
First Private [Member] \| As Recorded by IBERIABANK [Member]
Business Acquisition [Line Items]
Cash and cash equivalents	26,621
Investment securities	19,217
Loans	299,267
Core deposit intangible	506
Deferred tax asset	652
Other assets	5,148
Total Assets	351,411
Interest-bearing deposits	261,933
Non-interest-bearing deposits	50,334
Borrowings	6,451
Other liabilities	306
Total Liabilities	$ 319,024

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Amount of Interest-bearing deposits assumed at the acquisition date

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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.

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Amount of investments in debt and equity securities, including, but not limited to, held-to-maturity, trading and available-for-sale expected to be converted to cash, sold or exchanged within one year or the normal operating cycle, if longer, acquired at the acquisition date.

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Amount of deferred tax liability attributable to taxable temporary differences due after one year or the normal operating cycle, if longer, assumed at the acquisition date.

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The amount of identifiable intangible assets recognized as of the acquisition date.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

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Amount of liabilities assumed at the acquisition date.

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