Loans, Allowance for Loan and Lease Losses, and Reserve for Off-Balance Sheet Credit Commitments (Details 3) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Allowance for Loan and Lease Losses
Beginning Balance	$ 266,077,000	$ 263,356,000	$ 262,557,000	$ 257,007,000
Provision for credit losses, net of transfers	716,000	(1,618,000)	(254,000)	(1,796,000)
Charge-offs	(11,553,000)	(6,075,000)	(23,715,000)	(14,442,000)
Recoveries	14,294,000	10,270,000	30,946,000	25,164,000
Net (charge-offs) recoveries	2,741,000	4,195,000	7,231,000	10,722,000
Ending Balance	269,534,000	265,933,000	269,534,000	265,933,000
Allowance individually evaluated for impairment	7,550,000	11,068,000	7,550,000	11,068,000
Allowance collectively evaluated for impairment	261,984,000	254,865,000	261,984,000	254,865,000
Loans and leases, excluding covered loans	13,507,209,000	11,663,123,000	13,507,209,000	11,663,123,000	12,309,385,000
Loans and leases, individually evaluated for impairment	173,782,000	120,734,000	173,782,000	120,734,000
Loans and leases, collectively evaluated for impairment	13,333,427,000	11,542,389,000	13,333,427,000	11,542,389,000
Provision for credit losses in the allowance	1,000,000		1,000,000
Transfers to reserve for off-balance sheet credit commitments	300,000	1,600,000	1,300,000	1,800,000
Reserve for Off Balance Sheet Credit Commitments
Balance, beginning of period	24,067,000	21,707,000	23,097,000	21,529,000
Transfers from allowance for loan and lease losses	284,000	1,618,000	1,254,000	1,796,000
Balance, end of period	24,351,000	23,325,000	24,351,000	23,325,000
Commercial (includes lease financing)
Allowance for Loan and Lease Losses
Beginning Balance	84,087,000	75,661,000	82,965,000	82,451,000
Provision for credit losses, net of transfers	1,228,000	7,440,000	(2,933,000)	2,587,000
Charge-offs	(1,302,000)	(3,446,000)	(10,219,000)	(6,684,000)
Recoveries	9,394,000	6,062,000	23,594,000	7,363,000
Net (charge-offs) recoveries	8,092,000	2,616,000	13,375,000	679,000
Ending Balance	93,407,000	85,717,000	93,407,000	85,717,000
Allowance individually evaluated for impairment	2,850,000	7,605,000	2,850,000	7,605,000
Allowance collectively evaluated for impairment	90,557,000	78,112,000	90,557,000	78,112,000
Loans and leases, excluding covered loans	6,086,947,000	4,800,252,000	6,086,947,000	4,800,252,000
Loans and leases, individually evaluated for impairment	43,144,000	19,236,000	43,144,000	19,236,000
Loans and leases, collectively evaluated for impairment	6,043,803,000	4,781,016,000	6,043,803,000	4,781,016,000
Commercial real estate mortgages
Allowance for Loan and Lease Losses
Beginning Balance	46,586,000	47,519,000	45,967,000	52,516,000
Provision for credit losses, net of transfers	(51,000)	272,000	1,234,000	(10,937,000)
Charge-offs	(181,000)	(98,000)	(873,000)	(2,897,000)
Recoveries	1,294,000	1,367,000	1,320,000	10,378,000
Net (charge-offs) recoveries	1,113,000	1,269,000	447,000	7,481,000
Ending Balance	47,648,000	49,060,000	47,648,000	49,060,000
Allowance individually evaluated for impairment	2,282,000	1,150,000	2,282,000	1,150,000
Allowance collectively evaluated for impairment	45,366,000	47,910,000	45,366,000	47,910,000
Loans and leases, excluding covered loans	2,424,333,000	1,930,269,000	2,424,333,000	1,930,269,000	2,110,749,000
Loans and leases, individually evaluated for impairment	45,491,000	23,769,000	45,491,000	23,769,000
Loans and leases, collectively evaluated for impairment	2,378,842,000	1,906,500,000	2,378,842,000	1,906,500,000
Residential mortgage
Allowance for Loan and Lease Losses
Beginning Balance	13,803,000	13,527,000	14,029,000	16,753,000
Provision for credit losses, net of transfers	(846,000)	(401,000)	(578,000)	(3,012,000)
Charge-offs	(749,000)	(375,000)	(1,303,000)	(1,022,000)
Recoveries	206,000	122,000	266,000	154,000
Net (charge-offs) recoveries	(543,000)	(253,000)	(1,037,000)	(868,000)
Ending Balance	12,414,000	12,873,000	12,414,000	12,873,000
Allowance individually evaluated for impairment	398,000	56,000	398,000	56,000
Allowance collectively evaluated for impairment	12,016,000	12,817,000	12,016,000	12,817,000
Loans and leases, excluding covered loans	3,822,630,000	3,710,765,000	3,822,630,000	3,710,765,000	3,763,218,000
Loans and leases, individually evaluated for impairment	13,634,000	12,536,000	13,634,000	12,536,000
Loans and leases, collectively evaluated for impairment	3,808,996,000	3,698,229,000	3,808,996,000	3,698,229,000
Real estate construction
Allowance for Loan and Lease Losses
Beginning Balance	22,096,000	36,693,000	23,347,000	40,824,000
Provision for credit losses, net of transfers	326,000	(7,815,000)	(1,029,000)	(15,772,000)
Charge-offs	(7,858,000)	(1,897,000)	(9,459,000)	(2,463,000)
Recoveries	3,019,000	2,474,000	4,724,000	6,866,000
Net (charge-offs) recoveries	(4,839,000)	577,000	(4,735,000)	4,403,000
Ending Balance	17,583,000	29,455,000	17,583,000	29,455,000
Allowance individually evaluated for impairment	1,866,000	1,853,000	1,866,000	1,853,000
Allowance collectively evaluated for impairment	15,717,000	27,602,000	15,717,000	27,602,000
Loans and leases, excluding covered loans	301,829,000	355,014,000	301,829,000	355,014,000	315,609,000
Loans and leases, individually evaluated for impairment	66,529,000	60,630,000	66,529,000	60,630,000
Loans and leases, collectively evaluated for impairment	235,300,000	294,384,000	235,300,000	294,384,000
Equity lines of credit
Allowance for Loan and Lease Losses
Beginning Balance	8,032,000	6,445,000	8,024,000	7,229,000
Provision for credit losses, net of transfers	386,000	343,000	548,000	316,000
Charge-offs	(846,000)	(128,000)	(1,035,000)	(921,000)
Recoveries	38,000	8,000	73,000	44,000
Net (charge-offs) recoveries	(808,000)	(120,000)	(962,000)	(877,000)
Ending Balance	7,610,000	6,668,000	7,610,000	6,668,000
Allowance individually evaluated for impairment	154,000	404,000	154,000	404,000
Allowance collectively evaluated for impairment	7,456,000	6,264,000	7,456,000	6,264,000
Loans and leases, excluding covered loans	741,270,000	735,899,000	741,270,000	735,899,000	741,081,000
Loans and leases, individually evaluated for impairment	4,434,000	4,522,000	4,434,000	4,522,000
Loans and leases, collectively evaluated for impairment	736,836,000	731,377,000	736,836,000	731,377,000
Installment loan
Allowance for Loan and Lease Losses
Beginning Balance	1,938,000	5,445,000	1,959,000	3,931,000
Provision for credit losses, net of transfers	100,000	(3,600,000)	(338,000)	(1,884,000)
Charge-offs	(617,000)	(131,000)	(826,000)	(455,000)
Recoveries	343,000	237,000	969,000	359,000
Net (charge-offs) recoveries	(274,000)	106,000	143,000	(96,000)
Ending Balance	1,764,000	1,951,000	1,764,000	1,951,000
Allowance collectively evaluated for impairment	1,764,000	1,951,000	1,764,000	1,951,000
Loans and leases, excluding covered loans	130,200,000	130,924,000	130,200,000	130,924,000	132,647,000
Loans and leases, individually evaluated for impairment	550,000	41,000	550,000	41,000
Loans and leases, collectively evaluated for impairment	129,650,000	130,883,000	129,650,000	130,883,000
Unallocated
Allowance for Loan and Lease Losses
Beginning Balance	89,535,000	78,066,000	86,266,000	53,303,000
Provision for credit losses, net of transfers	(427,000)	2,143,000	2,842,000	26,906,000
Ending Balance	89,108,000	80,209,000	89,108,000	80,209,000
Allowance collectively evaluated for impairment	$ 89,108,000	$ 80,209,000	$ 89,108,000	$ 80,209,000