Loans, Allowance for Loan and Lease Losses, and Reserve for Off-Balance Sheet Credit Commitments (Details 3) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Allowance for Loan and Lease Losses
Beginning Balance	$ 269,534,000	$ 265,933,000	$ 262,557,000	$ 257,007,000
Provision for credit losses, net of transfers	1,091,000	7,999,000	837,000	6,203,000
Charge-offs	(14,124,000)	(15,172,000)	(37,838,000)	(29,613,000)
Recoveries	11,939,000	4,588,000	42,884,000	29,751,000
Net (charge-offs) recoveries	(2,185,000)	(10,584,000)	5,046,000	138,000
Ending Balance	268,440,000	263,348,000	268,440,000	263,348,000
Allowance individually evaluated for impairment	4,831,000	18,933,000	4,831,000	18,933,000
Allowance collectively evaluated for impairment	263,609,000	244,415,000	263,609,000	244,415,000
Loans and leases, excluding covered loans	13,724,651,000	12,164,209,000	13,724,651,000	12,164,209,000	12,309,385,000
Loans and leases, individually evaluated for impairment	165,817,000	158,060,000	165,817,000	158,060,000
Loans and leases, collectively evaluated for impairment	13,558,834,000	12,006,149,000	13,558,834,000	12,006,149,000
Provision for credit losses in the allowance	2,000,000	7,500,000	3,000,000	7,500,000
Transfers to or from reserve for off-balance sheet credit commitments	900,000	500,000	2,200,000	1,300,000
Reserve for Off Balance Sheet Credit Commitments
Balance, beginning of period	24,351,000	23,325,000	23,097,000	21,529,000
Transfers from (to) reserve for off-balance sheet credit commitments	909,000	(499,000)	2,163,000	1,297,000
Balance, end of period	25,260,000	22,826,000	25,260,000	22,826,000
Commercial (includes lease financing)
Allowance for Loan and Lease Losses
Beginning Balance	93,407,000	85,717,000	82,965,000	82,451,000
Provision for credit losses, net of transfers	6,293,000	2,772,000	3,360,000	5,359,000
Charge-offs	(12,163,000)	(6,282,000)	(22,382,000)	(12,966,000)
Recoveries	7,227,000	3,367,000	30,821,000	10,730,000
Net (charge-offs) recoveries	(4,936,000)	(2,915,000)	8,439,000	(2,236,000)
Ending Balance	94,764,000	85,574,000	94,764,000	85,574,000
Allowance individually evaluated for impairment	1,167,000	14,364,000	1,167,000	14,364,000
Allowance collectively evaluated for impairment	93,597,000	71,210,000	93,597,000	71,210,000
Loans and leases, excluding covered loans	6,264,562,000	5,166,802,000	6,264,562,000	5,166,802,000
Loans and leases, individually evaluated for impairment	34,731,000	32,036,000	34,731,000	32,036,000
Loans and leases, collectively evaluated for impairment	6,229,831,000	5,134,766,000	6,229,831,000	5,134,766,000
Commercial real estate mortgages
Allowance for Loan and Lease Losses
Beginning Balance	47,648,000	49,060,000	45,967,000	52,516,000
Provision for credit losses, net of transfers	(716,000)	(1,604,000)	518,000	(12,541,000)
Charge-offs	(444,000)	(1,231,000)	(1,318,000)	(4,127,000)
Recoveries	203,000	779,000	1,524,000	11,156,000
Net (charge-offs) recoveries	(241,000)	(452,000)	206,000	7,029,000
Ending Balance	46,691,000	47,004,000	46,691,000	47,004,000
Allowance individually evaluated for impairment	1,874,000	1,375,000	1,874,000	1,375,000
Allowance collectively evaluated for impairment	44,817,000	45,629,000	44,817,000	45,629,000
Loans and leases, excluding covered loans	2,463,664,000	2,059,114,000	2,463,664,000	2,059,114,000	2,110,749,000
Loans and leases, individually evaluated for impairment	58,217,000	25,899,000	58,217,000	25,899,000
Loans and leases, collectively evaluated for impairment	2,405,447,000	2,033,215,000	2,405,447,000	2,033,215,000
Residential mortgage
Allowance for Loan and Lease Losses
Beginning Balance	12,414,000	12,873,000	14,029,000	16,753,000
Provision for credit losses, net of transfers	1,318,000	(691,000)	740,000	(3,703,000)
Charge-offs	(1,030,000)	(245,000)	(2,333,000)	(1,267,000)
Recoveries	495,000	82,000	761,000	236,000
Net (charge-offs) recoveries	(535,000)	(163,000)	(1,572,000)	(1,031,000)
Ending Balance	13,197,000	12,019,000	13,197,000	12,019,000
Allowance individually evaluated for impairment	185,000	130,000	185,000	130,000
Allowance collectively evaluated for impairment	13,012,000	11,889,000	13,012,000	11,889,000
Loans and leases, excluding covered loans	3,897,690,000	3,742,768,000	3,897,690,000	3,742,768,000	3,763,218,000
Loans and leases, individually evaluated for impairment	11,342,000	10,254,000	11,342,000	10,254,000
Loans and leases, collectively evaluated for impairment	3,886,348,000	3,732,514,000	3,886,348,000	3,732,514,000
Real estate construction
Allowance for Loan and Lease Losses
Beginning Balance	17,583,000	29,455,000	23,347,000	40,824,000
Provision for credit losses, net of transfers	(4,425,000)	2,269,000	(5,454,000)	(13,503,000)
Charge-offs	(310,000)	(6,434,000)	(9,769,000)	(8,897,000)
Recoveries	3,415,000	201,000	8,139,000	7,067,000
Net (charge-offs) recoveries	3,105,000	(6,233,000)	(1,630,000)	(1,830,000)
Ending Balance	16,263,000	25,491,000	16,263,000	25,491,000
Allowance individually evaluated for impairment	1,467,000	2,989,000	1,467,000	2,989,000
Allowance collectively evaluated for impairment	14,796,000	22,502,000	14,796,000	22,502,000
Loans and leases, excluding covered loans	242,137,000	335,712,000	242,137,000	335,712,000	315,609,000
Loans and leases, individually evaluated for impairment	56,582,000	82,565,000	56,582,000	82,565,000
Loans and leases, collectively evaluated for impairment	185,555,000	253,147,000	185,555,000	253,147,000
Equity lines of credit
Allowance for Loan and Lease Losses
Beginning Balance	7,610,000	6,668,000	8,024,000	7,229,000
Provision for credit losses, net of transfers	43,000	(122,000)	591,000	194,000
Charge-offs	(43,000)	(523,000)	(1,077,000)	(1,443,000)
Recoveries	11,000	11,000	83,000	54,000
Net (charge-offs) recoveries	(32,000)	(512,000)	(994,000)	(1,389,000)
Ending Balance	7,621,000	6,034,000	7,621,000	6,034,000
Allowance individually evaluated for impairment	138,000	75,000	138,000	75,000
Allowance collectively evaluated for impairment	7,483,000	5,959,000	7,483,000	5,959,000
Loans and leases, excluding covered loans	718,966,000	728,890,000	718,966,000	728,890,000	741,081,000
Loans and leases, individually evaluated for impairment	4,496,000	6,653,000	4,496,000	6,653,000
Loans and leases, collectively evaluated for impairment	714,470,000	722,237,000	714,470,000	722,237,000
Installment loan
Allowance for Loan and Lease Losses
Beginning Balance	1,764,000	1,951,000	1,959,000	3,931,000
Provision for credit losses, net of transfers	(316,000)	417,000	(654,000)	(1,467,000)
Charge-offs	(134,000)	(457,000)	(959,000)	(913,000)
Recoveries	588,000	148,000	1,556,000	508,000
Net (charge-offs) recoveries	454,000	(309,000)	597,000	(405,000)
Ending Balance	1,902,000	2,059,000	1,902,000	2,059,000
Allowance collectively evaluated for impairment	1,902,000	2,059,000	1,902,000	2,059,000
Loans and leases, excluding covered loans	137,632,000	130,923,000	137,632,000	130,923,000	132,647,000
Loans and leases, individually evaluated for impairment	449,000	653,000	449,000	653,000
Loans and leases, collectively evaluated for impairment	137,183,000	130,270,000	137,183,000	130,270,000
Unallocated
Allowance for Loan and Lease Losses
Beginning Balance	89,108,000	80,209,000	86,266,000	53,303,000
Provision for credit losses, net of transfers	(1,106,000)	4,958,000	1,736,000	31,864,000
Ending Balance	88,002,000	85,167,000	88,002,000	85,167,000
Allowance collectively evaluated for impairment	$ 88,002,000	$ 85,167,000	$ 88,002,000	$ 85,167,000