Condensed Parent Company Only Financial Statements (Condensed Statements Of Cash Flows) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Net income	$ 53,538,000	$ 48,826,000	$ 158,354,000
Depreciation and amortization	16,772,000	11,042,000	10,377,000
Noncash compensation expense	9,114,000	7,797,000	6,586,000
Gain on sale of assets	(943,000)	76,000	644,000
Derivative (gains) losses on swaps	(1,911,000)	9,370,000
Cash retained from tax benefit associated with share-based payment arrangements	(1,454,000)	(637,000)	(1,346,000)
Other, net	1,625,000	(54,162,000)	25,225,000
Net Cash (Used in) Provided by Operating Activities	(41,363,000)	149,724,000	(122,956,000)
Cash received in excess of cash paid for acquisition	79,288,000	24,134,000	496,015,000
Proceeds from sale of premises and equipment	3,227,000	1,324,000	70,000
Purchases of premises and equipment	(44,055,000)	(38,063,000)	(16,212,000)
Net Cash Provided by (Used in) Investing Activities	82,853,000	7,617,000	(346,037,000)
Dividends paid to shareholders	(38,558,000)	(34,412,000)	(23,355,000)
Proceeds from long-term debt	3,176,000	45,233,000	53,531,000
Common stock issued	181,140,000	328,980,000	164,644,000
Repayments of long-term debt	(47,227,000)	(380,004,000)	(380,659,000)
Payments to repurchase common stock	(43,219,000)	(1,500,000)	(979,000)
Proceeds from sale of treasury stock for stock options exercised	6,807,000	1,631,000	4,449,000
Cash retained from tax benefit associated with share-based payment arrangements	1,454,000	637,000	1,346,000
Net Cash Provided by Financing Activities	194,028,000	5,040,000	298,525,000
Net Increase (Decrease) In Cash and Cash Equivalents	235,518,000	162,381,000	(170,468,000)
Cash and Cash Equivalents at Beginning of Period	337,778,000	175,397,000	345,865,000
Cash and Cash Equivalents at End of Period	573,296,000	337,778,000	175,397,000
IBERIABANK Corporation [Member]
Net income	53,538,000	48,826,000	158,354,000
Depreciation and amortization	1,071,000	(892,000)	(937,000)
Net income of subsidiaries	(70,983,000)	(72,616,000)	(171,845,000)
Noncash compensation expense	9,114,000	7,797,000	6,586,000
Gain on sale of assets		(3,000)
Derivative (gains) losses on swaps			(198,000)
Cash retained from tax benefit associated with share-based payment arrangements	(1,454,000)	(637,000)	(1,346,000)
Other, net	(23,278,000)	(5,953,000)	(13,649,000)
Net Cash (Used in) Provided by Operating Activities	(31,992,000)	(23,478,000)	(23,035,000)
Proceeds from sale of premises and equipment	10,000	3,000
Purchases of premises and equipment	(3,655,000)	(4,586,000)	(1,217,000)
Capital contributed to subsidiary	(12,963,000)	(94,561,000)	(130,730,000)
Acquisition		(733,000)
Net Cash Provided by (Used in) Investing Activities	(16,608,000)	(99,877,000)	(131,947,000)
Dividends paid to shareholders	(38,558,000)	(34,412,000)	(23,355,000)
Common stock issued		328,980,000	164,644,000
Preferred stock and common stock warrants (repaid) issued			(89,078,000)
Repayments of long-term debt	(13,500,000)		(8,333,000)
Payments to repurchase common stock	(43,219,000)	(1,500,000)	(979,000)
Proceeds from sale of treasury stock for stock options exercised	6,807,000	1,631,000	4,449,000
Cash retained from tax benefit associated with share-based payment arrangements	1,454,000	637,000	1,346,000
Net Cash Provided by Financing Activities	(87,016,000)	295,336,000	48,694,000
Net Increase (Decrease) In Cash and Cash Equivalents	(135,616,000)	171,981,000	(106,288,000)
Cash and Cash Equivalents at Beginning of Period	234,006,000	62,025,000	168,313,000
Cash and Cash Equivalents at End of Period	$ 98,390,000	$ 234,006,000	$ 62,025,000