Acquisition Of Whitney Holding Corporation (Narrative) (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Jun. 04, 2011
TARP stock redeemed	$ 307,700,000		$ 307,700,000
Purchase premium after adjusting for fair value of net assets acquired	514,000,000		514,000,000
Economies of scale expected from number of companies			2
Total purchase price					1,600,000,000
Fair value refinement period, maximum years			1
Business acquisition, purchase price allocation, total assets acquired	11,700,000,000		11,700,000,000
Business acquisition, purchase price allocation, loans and leases acquired	6,500,000,000		6,500,000,000
Business acquisition, purchase price allocation, investment securities acquired	2,600,000,000		2,600,000,000
Business acquisition, purchase price allocation, intangibles acquired	780,000,000		780,000,000
Business acquisition, purchase price allocation, liabilities assumed	10,100,000,000		10,100,000,000
Business acquisition, purchase price allocation, deposits assumed	9,200,000,000		9,200,000,000
Business acquisition, purchase price allocation, core deposit intangibles amount	189,000,000		189,000,000
Period for which the results of operations of the acquired entity are included in consolidated financial statements, in days			26
Business acquisition, effective date of acquisition			June 4, 2011
Business combination, net income of Acquirer included in consolidated statements			37,700,000
Business acquisition, merger related charges	4,400,000		4,400,000
Net income	20,000	19,000	36,000	70,000
Provision for credit losses			0
Merger related charges, total			22,200,000
Fair value of the acquired performing receivables					5,900,000,000
Gross contractual receivable	6,800,000,000		6,800,000,000
Estimate of the contractual cash flows not expected to be collected	400,000		400,000
Contingent liabilities payments to employees, fair value					59,600,000
Contractual contingency assumed liabilities for systems conversion and replacement initiative, fair value					14,000,000
Trade Names [Member]
Business acquisition, purchase price allocation, core deposit intangibles amount	54,000,000		54,000,000
Trust Relationship [Member]
Business acquisition, purchase price allocation, core deposit intangibles amount	11,000,000		11,000,000
Credit Card Relationship [Member]
Business acquisition, purchase price allocation, core deposit intangibles amount	11,000,000		11,000,000
Common Stock [Member]
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		$ 1,300,000,000