Loans, Allowance for Loan and Lease Losses, and Reserve for Off-Balance Sheet Credit Commitments (Details 3) (USD $)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Allowance for Loan and Lease Losses
Beginning Balance	$ 262,557,000	$ 257,007,000
Provision for credit losses, net of transfers	(970,000)	(178,000)
Charge-offs	(12,162,000)	(8,367,000)
Recoveries	16,652,000	14,894,000
Net (charge-offs) recoveries	4,490,000	6,527,000
Ending Balance	266,077,000	263,356,000
Allowance individually evaluated for impairment	14,118,000	8,655,000
Allowance collectively evaluated for impairment	251,959,000	254,701,000
Loans and leases, excluding covered loans	12,747,902,000	11,269,684,000	12,309,385,000
Loans and leases, individually evaluated for impairment	150,937,000	145,488,000
Loans and leases, collectively evaluated for impairment	12,596,965,000	11,124,196,000
Transfers to reserve for off-balance sheet credit commitments	1,000,000	200,000
Reserve for Off Balance Sheet Credit Commitments
Balance, beginning of period	23,097,000	21,529,000
Transfers from allowance for loan and lease losses	970,000	178,000
Balance, end of period	24,067,000	21,707,000
Commercial (includes lease financing)
Allowance for Loan and Lease Losses
Beginning Balance	82,965,000	82,451,000
Provision for credit losses, net of transfers	(4,161,000)	(4,853,000)
Charge-offs	(8,917,000)	(3,238,000)
Recoveries	14,200,000	1,301,000
Net (charge-offs) recoveries	5,283,000	(1,937,000)
Ending Balance	84,087,000	75,661,000
Allowance individually evaluated for impairment	3,335,000	2,291,000
Allowance collectively evaluated for impairment	80,752,000	73,370,000
Loans and leases, excluding covered loans	5,573,782,000	4,468,177,000
Loans and leases, individually evaluated for impairment	40,415,000	14,431,000
Loans and leases, collectively evaluated for impairment	5,533,367,000	4,453,746,000
Commercial real estate mortgages
Allowance for Loan and Lease Losses
Beginning Balance	45,967,000	52,516,000
Provision for credit losses, net of transfers	1,285,000	(11,209,000)
Charge-offs	(692,000)	(2,799,000)
Recoveries	26,000	9,011,000
Net (charge-offs) recoveries	(666,000)	6,212,000
Ending Balance	46,586,000	47,519,000
Allowance individually evaluated for impairment	1,019,000	1,060,000
Allowance collectively evaluated for impairment	45,567,000	46,459,000
Loans and leases, excluding covered loans	2,213,114,000	1,902,862,000	2,110,749,000
Loans and leases, individually evaluated for impairment	22,306,000	25,790,000
Loans and leases, collectively evaluated for impairment	2,190,808,000	1,877,072,000
Residential mortgage
Allowance for Loan and Lease Losses
Beginning Balance	14,029,000	16,753,000
Provision for credit losses, net of transfers	268,000	(2,611,000)
Charge-offs	(554,000)	(647,000)
Recoveries	60,000	32,000
Net (charge-offs) recoveries	(494,000)	(615,000)
Ending Balance	13,803,000	13,527,000
Allowance individually evaluated for impairment	331,000	384,000
Allowance collectively evaluated for impairment	13,472,000	13,143,000
Loans and leases, excluding covered loans	3,805,807,000	3,603,058,000	3,763,218,000
Loans and leases, individually evaluated for impairment	13,000,000	12,476,000
Loans and leases, collectively evaluated for impairment	3,792,807,000	3,590,582,000
Real estate construction
Allowance for Loan and Lease Losses
Beginning Balance	23,347,000	40,824,000
Provision for credit losses, net of transfers	(1,355,000)	(7,957,000)
Charge-offs	(1,601,000)	(566,000)
Recoveries	1,705,000	4,392,000
Net (charge-offs) recoveries	104,000	3,826,000
Ending Balance	22,096,000	36,693,000
Allowance individually evaluated for impairment	9,395,000	334,000
Allowance collectively evaluated for impairment	12,701,000	36,359,000
Loans and leases, excluding covered loans	313,409,000	415,241,000	315,609,000
Loans and leases, individually evaluated for impairment	67,686,000	81,604,000
Loans and leases, collectively evaluated for impairment	245,723,000	333,637,000
Equity lines of credit
Allowance for Loan and Lease Losses
Beginning Balance	8,024,000	7,229,000
Provision for credit losses, net of transfers	162,000	(27,000)
Charge-offs	(189,000)	(793,000)
Recoveries	35,000	36,000
Net (charge-offs) recoveries	(154,000)	(757,000)
Ending Balance	8,032,000	6,445,000
Allowance individually evaluated for impairment	38,000	72,000
Allowance collectively evaluated for impairment	7,994,000	6,373,000
Loans and leases, excluding covered loans	715,997,000	733,567,000	741,081,000
Loans and leases, individually evaluated for impairment	6,980,000	4,249,000
Loans and leases, collectively evaluated for impairment	709,017,000	729,318,000
Installment loan
Allowance for Loan and Lease Losses
Beginning Balance	1,959,000	3,931,000
Provision for credit losses, net of transfers	(438,000)	1,716,000
Charge-offs	(209,000)	(324,000)
Recoveries	626,000	122,000
Net (charge-offs) recoveries	417,000	(202,000)
Ending Balance	1,938,000	5,445,000
Allowance individually evaluated for impairment		4,514,000
Allowance collectively evaluated for impairment	1,938,000	931,000
Loans and leases, excluding covered loans	125,793,000	146,779,000	132,647,000
Loans and leases, individually evaluated for impairment	550,000	6,938,000
Loans and leases, collectively evaluated for impairment	125,243,000	139,841,000
Unallocated
Allowance for Loan and Lease Losses
Beginning Balance	86,266,000	53,303,000
Provision for credit losses, net of transfers	3,269,000	24,763,000
Ending Balance	89,535,000	78,066,000
Allowance collectively evaluated for impairment	$ 89,535,000	$ 78,066,000