Loans, Allowance for Loan and Lease Losses, and Reserve for Off-Balance Sheet Credit Commitments (Details 4) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Allowance for Loan and Lease Losses
Beginning Balance	$ 289,914,000	$ 269,534,000	$ 277,888,000	$ 262,557,000
Provision (reduction) for credit losses, net of transfers	(749,000)	1,091,000	(1,036,000)	837,000
Charge-offs	(2,001,000)	(14,124,000)	(7,110,000)	(37,838,000)
Recoveries	8,783,000	11,939,000	26,205,000	42,884,000
Net recoveries (charge-offs)	6,782,000	(2,185,000)	19,095,000	5,046,000
Ending Balance	295,947,000	268,440,000	295,947,000	268,440,000
Allowance individually evaluated for impairment	1,178,000	4,831,000	1,178,000	4,831,000
Allowance collectively evaluated for impairment	294,769,000	263,609,000	294,769,000	263,609,000
Loans and leases, excluding covered loans	16,566,133,000	13,724,651,000	16,566,133,000	13,724,651,000	14,818,295,000
Loans and leases, individually evaluated for impairment	110,580,000	165,817,000	110,580,000	165,817,000
Loans and leases, collectively evaluated for impairment	16,455,553,000	13,558,834,000	16,455,553,000	13,558,834,000
Provision for credit losses in the allowance	0	2,000,000	0	3,000,000
Transfers to or from reserve for off-balance sheet credit commitments	700,000	900,000	1,000,000	2,200,000
Reserve for Off Balance Sheet Credit Commitments
Balance, beginning of period	25,124,000	24,351,000	24,837,000	23,097,000
Transfers from allowance for loan and lease losses	749,000	909,000	1,036,000	2,163,000
Balance, end of period	25,873,000	25,260,000	25,873,000	25,260,000
Commercial (includes lease financing)
Allowance for Loan and Lease Losses
Beginning Balance	116,619,000	93,981,000	104,731,000	83,514,000
Provision (reduction) for credit losses, net of transfers	(14,173,000)	6,333,000	(7,313,000)	3,425,000
Charge-offs	(488,000)	(12,163,000)	(4,719,000)	(22,382,000)
Recoveries	4,863,000	7,227,000	14,122,000	30,821,000
Net recoveries (charge-offs)	4,375,000	(4,936,000)	9,403,000	8,439,000
Ending Balance	106,821,000	95,378,000	106,821,000	95,378,000
Allowance individually evaluated for impairment	344,000	1,167,000	344,000	1,167,000
Allowance collectively evaluated for impairment	106,477,000	94,211,000	106,477,000	94,211,000
Loans and leases, excluding covered loans	7,856,244,000	6,264,562,000	7,856,244,000	6,264,562,000
Loans and leases, individually evaluated for impairment	32,727,000	34,731,000	32,727,000	34,731,000
Loans and leases, collectively evaluated for impairment	7,823,517,000	6,229,831,000	7,823,517,000	6,229,831,000
Commercial real estate mortgages
Allowance for Loan and Lease Losses
Beginning Balance	53,339,000	49,715,000	48,901,000	48,451,000
Provision (reduction) for credit losses, net of transfers	(2,829,000)	(1,298,000)	572,000	(481,000)
Charge-offs	(1,270,000)	(444,000)	(1,315,000)	(1,318,000)
Recoveries	686,000	203,000	1,768,000	1,524,000
Net recoveries (charge-offs)	(584,000)	(241,000)	453,000	206,000
Ending Balance	49,926,000	48,176,000	49,926,000	48,176,000
Allowance individually evaluated for impairment	602,000	1,874,000	602,000	1,874,000
Allowance collectively evaluated for impairment	49,324,000	46,302,000	49,324,000	46,302,000
Loans and leases, excluding covered loans	3,077,183,000	2,436,218,000	3,077,183,000	2,436,218,000	2,739,284,000
Loans and leases, individually evaluated for impairment	38,546,000	58,217,000	38,546,000	58,217,000
Loans and leases, collectively evaluated for impairment	3,038,637,000	2,378,001,000	3,038,637,000	2,378,001,000
Residential mortgage
Allowance for Loan and Lease Losses
Beginning Balance	8,004,000	12,490,000	10,558,000	14,122,000
Provision (reduction) for credit losses, net of transfers	5,070,000	1,327,000	2,547,000	732,000
Charge-offs		(1,030,000)	(106,000)	(2,333,000)
Recoveries	40,000	495,000	115,000	761,000
Net recoveries (charge-offs)	40,000	(535,000)	9,000	(1,572,000)
Ending Balance	13,114,000	13,282,000	13,114,000	13,282,000
Allowance individually evaluated for impairment	232,000	185,000	232,000	185,000
Allowance collectively evaluated for impairment	12,882,000	13,097,000	12,882,000	13,097,000
Loans and leases, excluding covered loans	4,418,231,000	3,897,690,000	4,418,231,000	3,897,690,000	3,962,205,000
Loans and leases, individually evaluated for impairment	6,767,000	11,342,000	6,767,000	11,342,000
Loans and leases, collectively evaluated for impairment	4,411,464,000	3,886,348,000	4,411,464,000	3,886,348,000
Real estate construction
Allowance for Loan and Lease Losses
Beginning Balance	8,335,000	14,810,000	11,784,000	20,155,000
Provision (reduction) for credit losses, net of transfers	(1,589,000)	(3,898,000)	(10,386,000)	(4,508,000)
Charge-offs		(310,000)	(100,000)	(9,769,000)
Recoveries	2,945,000	3,415,000	8,393,000	8,139,000
Net recoveries (charge-offs)	2,945,000	3,105,000	8,293,000	(1,630,000)
Ending Balance	9,691,000	14,017,000	9,691,000	14,017,000
Allowance individually evaluated for impairment		1,467,000		1,467,000
Allowance collectively evaluated for impairment	9,691,000	12,550,000	9,691,000	12,550,000
Loans and leases, excluding covered loans	380,489,000	269,583,000	380,489,000	269,583,000	313,190,000
Loans and leases, individually evaluated for impairment	30,190,000	56,582,000	30,190,000	56,582,000
Loans and leases, collectively evaluated for impairment	350,299,000	213,001,000	350,299,000	213,001,000
Home Equity Loans and Lines of Credit
Allowance for Loan and Lease Losses
Beginning Balance	5,400,000	7,656,000	7,283,000	8,077,000
Provision (reduction) for credit losses, net of transfers	3,092,000	47,000	946,000	588,000
Charge-offs	(225,000)	(43,000)	(500,000)	(1,077,000)
Recoveries	31,000	11,000	569,000	83,000
Net recoveries (charge-offs)	(194,000)	(32,000)	69,000	(994,000)
Ending Balance	8,298,000	7,671,000	8,298,000	7,671,000
Allowance individually evaluated for impairment		138,000		138,000
Allowance collectively evaluated for impairment	8,298,000	7,533,000	8,298,000	7,533,000
Loans and leases, excluding covered loans	681,879,000	718,966,000	681,879,000	718,966,000	711,750,000
Loans and leases, individually evaluated for impairment	2,350,000	4,496,000	2,350,000	4,496,000
Loans and leases, collectively evaluated for impairment	679,529,000	714,470,000	679,529,000	714,470,000
Installment loan
Allowance for Loan and Lease Losses
Beginning Balance	1,355,000	1,774,000	1,858,000	1,972,000
Provision (reduction) for credit losses, net of transfers	317,000	(314,000)	(854,000)	(655,000)
Charge-offs	(18,000)	(134,000)	(370,000)	(959,000)
Recoveries	218,000	588,000	1,238,000	1,556,000
Net recoveries (charge-offs)	200,000	454,000	868,000	597,000
Ending Balance	1,872,000	1,914,000	1,872,000	1,914,000
Allowance collectively evaluated for impairment	1,872,000	1,914,000	1,872,000	1,914,000
Loans and leases, excluding covered loans	152,107,000	137,632,000	152,107,000	137,632,000	142,793,000
Loans and leases, individually evaluated for impairment		449,000		449,000
Loans and leases, collectively evaluated for impairment	152,107,000	137,183,000	152,107,000	137,183,000
Unallocated
Allowance for Loan and Lease Losses
Beginning Balance	96,862,000	89,108,000	92,773,000	86,266,000
Provision (reduction) for credit losses, net of transfers	9,363,000	(1,106,000)	13,452,000	1,736,000
Ending Balance	106,225,000	88,002,000	106,225,000	88,002,000
Allowance collectively evaluated for impairment	$ 106,225,000	$ 88,002,000	$ 106,225,000	$ 88,002,000