Loans (Details) (USD $)										3 Months Ended
	Mar. 31, 2012		Dec. 31, 2011		Mar. 31, 2011		Mar. 31, 2012 Acquired Loans Noncovered [Member]	Dec. 31, 2011 Acquired Loans Noncovered [Member]	Mar. 31, 2011 Acquired Loans Noncovered [Member]	Mar. 31, 2012 Loss Share Receivable [Member]	Mar. 31, 2011 Loss Share Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing							$ 0	$ 3,000	$ 26,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing Guaranteed By US Government	3,300,000		3,000,000		2,300,000
Loans and Leases Receivable, Gross, Commercial	5,220,051,000		5,107,747,000		4,565,376,000
Loans and Leases Receivable, Gross, Consumer, Mortgage	428,950,000		413,664,000		399,380,000
Loans and Leases Receivable, Gross, Consumer, Installment, Other	1,259,930,000		1,263,665,000		1,282,170,000
Loans and Leases Receivable, Gross, Consumer, Home Equity	739,548,000		743,982,000		736,947,000
Loans and Leases Receivable, Gross, Consumer, Revolving, Credit Card	140,618,000		146,356,000		141,864,000
Loans and Leases Receivable, Gross, Consumer, Lease Financing	74,112,000		73,530,000		60,487,000
Total noncovered loans	7,863,209,000	[1]	7,748,944,000	[1]	7,186,224,000	[1]	99,200,000	113,200,000	196,300,000
Loans and Leases Receivable, Allowance	103,849,000		107,699,000		114,690,000
Net noncovered loans	7,759,360,000		7,641,245,000		7,071,534,000
Covered Loans and Leases Receivable Gross	1,378,150,000	[2]	1,497,140,000	[2]	1,870,255,000	[2]				171,136,000	265,981,000
Covered Certain Loans Acquired in Transfer not Accounted for as Debt Securities Allowance for Loan Losses	41,070,000		36,417,000		28,405,000
Covered Loans and Leases Receivable Net	1,337,080,000		1,460,723,000		1,841,850,000
Net loans	9,096,440,000		9,101,968,000		8,913,384,000
Changes in Loss Share Receivable Associated with Covered Loans [Roll Forward]
Balance at beginning of period	1,378,150,000	[2]	1,497,140,000	[2]	1,870,255,000	[2]				205,664,000	288,605,000
Accretion										(9,657,000)	(11,630,000)
Increase due to impairment										4,899,000	15,179,000
FDIC reimbursement										(27,430,000)	(25,631,000)
Covered loans paid in full										(2,340,000)	(542,000)
Balance at end of the period	$ 1,378,150,000	[2]	$ 1,497,140,000	[2]	$ 1,870,255,000	[2]				$ 171,136,000	$ 265,981,000

[1] (a)Includes acquired, noncovered loans of $99.2 million, $113.2 million, and $196.3 million as of March 31, 2012,December 31, 2011 and March 31, 2011, respectively.

[2] Includes loss share receivable of $171.1 million, $205.7 million, and $266.0 million as of March 31, 2012, December 31, 2011 and March 31, 2011, respectively.