Acquisitions - Net Assets Acquired Liabilities Assumed and Consideration Transferred at Fair Value (Detail) (USD $)	12 Months Ended		12 Months Ended
	Dec. 31, 2011	Jun. 04, 2011	Dec. 31, 2012 Fair Value of Net Assets Acquired at Date of Acquisition [Member] Whitney Holding Corporation [Member]	Dec. 31, 2012 Subsequent Acquisition-Date Adjustments [Member] Whitney Holding Corporation [Member]	Dec. 31, 2012 Business Acquisition Acquire [Member] Whitney Holding Corporation [Member]
ASSETS
Cash and cash equivalents			$ 957,000,000		$ 957,000,000
Loans held for sale			57,000,000		57,000,000
Securities			2,635,000,000	1,000,000	2,636,000,000
Loans and leases			6,456,000,000	(9,000,000)	6,447,000,000
Property and equipment			284,000,000	(21,000,000)	263,000,000
Other intangible assets		224,000,000	266,000,000	(42,000,000)	224,000,000
Other assets			580,000,000	(7,000,000)	573,000,000
Total identifiable assets			11,235,000,000	(78,000,000)	11,157,000,000
LIABILITIES
Deposits		9,200,000,000	9,182,000,000		9,182,000,000
Borrowings			776,000,000		776,000,000
Other liabilities			175,000,000	(3,000,000)	172,000,000
Total liabilities		10,100,000,000	10,133,000,000	(3,000,000)	10,130,000,000
Net identifiable assets acquired			1,102,000,000	(75,000,000)	1,027,000,000
Goodwill	513,917,000		514,000,000	75,000,000	589,000,000
Net assets acquired	11,200,000,000		1,616,000,000		1,616,000,000
CONSIDERATION:
Hancock Holding Company common shares issued	40,794,261		41,000,000
Purchase price per share of the Company's common stock			$ 32.04
Company common stock issued and cash exchanged for fractional shares			1,307,000,000
Stock options converted			1,000,000
Cash paid for TARP preferred stock and warrants			308,000,000
Fair value of total consideration transferred		$ 1,600,000,000	$ 1,616,000,000