Whitney Acquisition (Details Textual) (USD $)	3 Months Ended				3 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Jun. 04, 2011	Mar. 31, 2011	Mar. 31, 2012 Common Stock	Sep. 16, 2011 Mississippi Gulf Coast [Member]	Sep. 16, 2011 Bogalusa La [Member]	Sep. 16, 2011 Whitney Bank Divested Branches [Member]	Mar. 31, 2012 Whitney [Member]
Acquisitions (Textual) [Abstract]
Shares in Hancock for each share of Whitney					0.418
Business acquisition, number of shares issued					40,794,261
Business acquisition, fair value of shares issued					$ 1,300,000,000
TARP stock redeemed			307,700,000
Business acquisition costs			1,600,000,000						5,900,000
Number of bank branches divested						7	1
Loans	11,146,076,000	11,191,901,000						47,000,000
Deposits	15,432,767,000	15,713,579,000						180,000,000
Fair value refinement period, maximum years	1 year
Business acquisition, purchase price allocation, total assets acquired	11,200,000,000
Business acquisition, purchase price allocation, loans and leases acquired	6,500,000,000
Business acquisition, purchase price allocation, investment securities acquired	2,600,000,000
Business acquisition, purchase price allocation, intangibles acquired	224,000,000
Business acquisition, purchase price allocation, liabilities assumed	10,100,000,000
Business Acquisition, Purchase Price Allocation, Deposits Assumed	9,200,000,000
Business Acquisition, Purchase Price Allocation, goodwill amount	589,000,000
Business acquisition, merger related charges	$ 33,900,000			$ 1,600,000