Loans, Allowance for Loan and Lease Losses, and Reserve for Off-Balance Sheet Credit Commitments (Details 4) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Allowance for Loan and Lease Losses
Beginning Balance	$ 282,328,000	$ 266,077,000	$ 277,888,000	$ 262,557,000
Provision for credit losses, net of transfers	81,000	716,000	(287,000)	(254,000)
Charge-offs	(3,086,000)	(11,553,000)	(5,109,000)	(23,715,000)
Recoveries	10,591,000	14,294,000	17,422,000	30,946,000
Net (charge-offs) recoveries	7,505,000	2,741,000	12,313,000	7,231,000
Ending Balance	289,914,000	269,534,000	289,914,000	269,534,000
Allowance individually evaluated for impairment	2,960,000	7,550,000	2,960,000	7,550,000
Allowance collectively evaluated for impairment	286,954,000	261,984,000	286,954,000	261,984,000
Loans and leases, excluding covered loans	15,819,252,000	13,507,209,000	15,819,252,000	13,507,209,000	14,818,295,000
Loans and leases, individually evaluated for impairment	118,529,000	173,782,000	118,529,000	173,782,000
Loans and leases, collectively evaluated for impairment	15,700,723,000	13,333,427,000	15,700,723,000	13,333,427,000
Provision for credit losses in the allowance	0	1,000,000	0	1,000,000
Transfers to or from reserve for off-balance sheet credit commitments	(100,000)	300,000	300,000	1,300,000
Reserve for Off Balance Sheet Credit Commitments
Balance, beginning of period	25,205,000	24,067,000	24,837,000	23,097,000
Transfers (to) from allowance for loan and lease losses	(81,000)	284,000	287,000	1,254,000
Balance, end of period	25,124,000	24,351,000	25,124,000	24,351,000
Commercial (includes lease financing)
Allowance for Loan and Lease Losses
Beginning Balance	112,397,000	84,087,000	104,156,000	82,965,000
Provision for credit losses, net of transfers	1,091,000	1,228,000	7,159,000	(2,933,000)
Charge-offs	(2,869,000)	(1,302,000)	(4,231,000)	(10,219,000)
Recoveries	5,724,000	9,394,000	9,259,000	23,594,000
Net (charge-offs) recoveries	2,855,000	8,092,000	5,028,000	13,375,000
Ending Balance	116,343,000	93,407,000	116,343,000	93,407,000
Allowance individually evaluated for impairment	478,000	2,850,000	478,000	2,850,000
Allowance collectively evaluated for impairment	115,865,000	90,557,000	115,865,000	90,557,000
Loans and leases, excluding covered loans	7,497,105,000	6,086,947,000	7,497,105,000	6,086,947,000
Loans and leases, individually evaluated for impairment	34,915,000	43,144,000	34,915,000	43,144,000
Loans and leases, collectively evaluated for impairment	7,462,190,000	6,043,803,000	7,462,190,000	6,043,803,000
Commercial real estate mortgages
Allowance for Loan and Lease Losses
Beginning Balance	52,494,000	46,586,000	48,240,000	45,967,000
Provision for credit losses, net of transfers	736,000	(51,000)	4,987,000	1,234,000
Charge-offs		(181,000)	(45,000)	(873,000)
Recoveries	1,034,000	1,294,000	1,082,000	1,320,000
Net (charge-offs) recoveries	1,034,000	1,113,000	1,037,000	447,000
Ending Balance	54,264,000	47,648,000	54,264,000	47,648,000
Allowance individually evaluated for impairment	2,252,000	2,282,000	2,252,000	2,282,000
Allowance collectively evaluated for impairment	52,012,000	45,366,000	52,012,000	45,366,000
Loans and leases, excluding covered loans	3,101,169,000	2,424,333,000	3,101,169,000	2,424,333,000	2,829,694,000
Loans and leases, individually evaluated for impairment	41,932,000	45,491,000	41,932,000	45,491,000
Loans and leases, collectively evaluated for impairment	3,059,237,000	2,378,842,000	3,059,237,000	2,378,842,000
Residential mortgage
Allowance for Loan and Lease Losses
Beginning Balance	7,230,000	13,803,000	10,499,000	14,029,000
Provision for credit losses, net of transfers	718,000	(846,000)	(2,483,000)	(578,000)
Charge-offs	(1,000)	(749,000)	(106,000)	(1,303,000)
Recoveries	38,000	206,000	75,000	266,000
Net (charge-offs) recoveries	37,000	(543,000)	(31,000)	(1,037,000)
Ending Balance	7,985,000	12,414,000	7,985,000	12,414,000
Allowance individually evaluated for impairment	230,000	398,000	230,000	398,000
Allowance collectively evaluated for impairment	7,755,000	12,016,000	7,755,000	12,016,000
Loans and leases, excluding covered loans	4,153,051,000	3,822,630,000	4,153,051,000	3,822,630,000	3,962,205,000
Loans and leases, individually evaluated for impairment	7,979,000	13,634,000	7,979,000	13,634,000
Loans and leases, collectively evaluated for impairment	4,145,072,000	3,808,996,000	4,145,072,000	3,808,996,000
Real estate construction
Allowance for Loan and Lease Losses
Beginning Balance	9,876,000	22,096,000	13,130,000	23,347,000
Provision for credit losses, net of transfers	(4,837,000)	326,000	(10,757,000)	(1,029,000)
Charge-offs	(100,000)	(7,858,000)	(100,000)	(9,459,000)
Recoveries	2,782,000	3,019,000	5,448,000	4,724,000
Net (charge-offs) recoveries	2,682,000	(4,839,000)	5,348,000	(4,735,000)
Ending Balance	7,721,000	17,583,000	7,721,000	17,583,000
Allowance individually evaluated for impairment		1,866,000		1,866,000
Allowance collectively evaluated for impairment	7,721,000	15,717,000	7,721,000	15,717,000
Loans and leases, excluding covered loans	217,808,000	301,829,000	217,808,000	301,829,000	222,780,000
Loans and leases, individually evaluated for impairment	30,446,000	66,529,000	30,446,000	66,529,000
Loans and leases, collectively evaluated for impairment	187,362,000	235,300,000	187,362,000	235,300,000
Home Equity Loans and Lines of Credit
Allowance for Loan and Lease Losses
Beginning Balance	4,828,000	8,032,000	7,243,000	8,024,000
Provision for credit losses, net of transfers	185,000	386,000	(2,118,000)	548,000
Charge-offs	(35,000)	(846,000)	(275,000)	(1,035,000)
Recoveries	410,000	38,000	538,000	73,000
Net (charge-offs) recoveries	375,000	(808,000)	263,000	(962,000)
Ending Balance	5,388,000	7,610,000	5,388,000	7,610,000
Allowance individually evaluated for impairment		154,000		154,000
Allowance collectively evaluated for impairment	5,388,000	7,456,000	5,388,000	7,456,000
Loans and leases, excluding covered loans	700,681,000	741,270,000	700,681,000	741,270,000	711,750,000
Loans and leases, individually evaluated for impairment	3,257,000	4,434,000	3,257,000	4,434,000
Loans and leases, collectively evaluated for impairment	697,424,000	736,836,000	697,424,000	736,836,000
Installment loan
Allowance for Loan and Lease Losses
Beginning Balance	1,222,000	1,938,000	1,847,000	1,959,000
Provision for credit losses, net of transfers	(393,000)	100,000	(1,164,000)	(338,000)
Charge-offs	(81,000)	(617,000)	(352,000)	(826,000)
Recoveries	603,000	343,000	1,020,000	969,000
Net (charge-offs) recoveries	522,000	(274,000)	668,000	143,000
Ending Balance	1,351,000	1,764,000	1,351,000	1,764,000
Allowance collectively evaluated for impairment	1,351,000	1,764,000	1,351,000	1,764,000
Loans and leases, excluding covered loans	149,438,000	130,200,000	149,438,000	130,200,000	142,793,000
Loans and leases, individually evaluated for impairment		550,000		550,000
Loans and leases, collectively evaluated for impairment	149,438,000	129,650,000	149,438,000	129,650,000
Unallocated
Allowance for Loan and Lease Losses
Beginning Balance	94,281,000	89,535,000	92,773,000	86,266,000
Provision for credit losses, net of transfers	2,581,000	(427,000)	4,089,000	2,842,000
Ending Balance	96,862,000	89,108,000	96,862,000	89,108,000
Allowance collectively evaluated for impairment	$ 96,862,000	$ 89,108,000	$ 96,862,000	$ 89,108,000