Loans (Details) (USD $)	9 Months Ended									3 Months Ended		9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Dec. 31, 2011		Sep. 30, 2012 Acquired Loans Noncovered [Member]	Dec. 31, 2011 Acquired Loans Noncovered [Member]	Sep. 30, 2011 Acquired Loans Noncovered [Member]	Sep. 30, 2012 Loss Share Receivable [Member]	Sep. 30, 2011 Loss Share Receivable [Member]	Sep. 30, 2012 Loss Share Receivable [Member]	Sep. 30, 2011 Loss Share Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds from Sale of Mortgage Loans Held-for-sale	588.6		324.8
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing							$ 132,000	$ 3,000	$ 395,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing Guaranteed By US Government	3,100,000		2,600,000		3,000,000
Loans and Leases Receivable, Gross, Commercial	5,511,678,000		5,018,857,000		5,107,747,000
Loans and Leases Receivable, Gross, Consumer, Mortgage	439,062,000		397,309,000		413,664,000
Loans and Leases Receivable, Gross, Consumer, Installment, Other	1,321,081,000		1,271,327,000		1,263,665,000
Loans and Leases Receivable, Gross, Consumer, Home Equity	789,743,000		743,377,000		743,982,000
Loans and Leases Receivable, Gross, Consumer, Revolving, Credit Card	143,918,000		142,710,000		146,356,000
Loans and Leases Receivable, Gross, Consumer, Lease Financing	110,938,000		57,992,000		73,530,000
Total noncovered loans	8,316,420,000	[1]	7,631,572,000	[1]	7,748,944,000	[1]	56,000,000	113,200,000	178,000,000
Loans and Leases Receivable, Allowance	(98,942,000)		(109,187,000)		(107,699,000)
Net noncovered loans	8,217,478,000		7,522,385,000		7,641,245,000
Covered Loans and Leases Receivable Gross	1,174,929,000	[2]	1,647,218,000	[2]						131,872,000	220,471,000	131,872,000	220,471,000
Covered Certain Loans Acquired in Transfer not Accounted for as Debt Securities Allowance for Loan Losses	43,644,000		34,603,000		36,417,000
Covered Loans and Leases Receivable Net	1,131,285,000		1,612,615,000		1,460,723,000
Net loans	9,348,763,000		9,135,000,000		9,101,968,000
Changes in Loss Share Receivable Associated with Covered Loans [Roll Forward]
Balance at beginning of period	1,497,140,000									152,615,000	239,424,000	205,664,000	288,605,000
Accretion										(8,401,000)	(9,322,000)	(26,935,000)	(30,821,000)
Increase due to impairment										1,484,000	8,224,000	12,601,000	31,077,000
FDIC reimbursement										(12,597,000)	(14,493,000)	(50,678,000)	(62,895,000)
Covered loans paid in full										(1,229,000)	(3,362,000)	(8,780,000)	(5,495,000)
Balance at end of the period	1,174,929,000	[2]	1,647,218,000	[2]						131,872,000	220,471,000	131,872,000	220,471,000
Covered Loans Loss Share Receivable	$ 131,872,000		$ 220,471,000		$ 205,664,000

[1] (a)Includes acquired, noncovered loans of $56.0 million, $113.2 million and $178.0 million as of September 30, 2012, December 31, 2011 and September 30, 2011, respectively.

[2] Includes loss share receivable of $131.9 million, $205.7 million and $220.5 million as of September 30, 2012, December 31, 2011 and September 30, 2011, respectively.