Loans, Allowance for Loan and Lease Losses, and Reserve for Off-Balance Sheet Credit Commitments (Details 4) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Allowance for Loan and Lease Losses
Beginning Balance	$ 277,888,000	$ 262,557,000
Provision for credit losses, net of transfers	(368,000)	(970,000)
Charge-offs	(2,023,000)	(12,162,000)
Recoveries	6,831,000	16,652,000
Net (charge-offs) recoveries	4,808,000	4,490,000
Ending Balance	282,328,000	266,077,000
Allowance individually evaluated for impairment	2,884,000	14,118,000
Allowance collectively evaluated for impairment	279,444,000	251,959,000
Loans and leases, excluding covered loans	15,216,906,000	12,747,902,000	14,818,295,000
Loans and leases, individually evaluated for impairment	123,835,000	150,937,000
Loans and leases, collectively evaluated for impairment	15,093,071,000	12,596,965,000
Transfers to or from reserve for off-balance sheet credit commitments	400,000	1,000,000
Provision for credit losses in the allowance	0	0
Reserve for Off Balance Sheet Credit Commitments
Balance, beginning of period	24,837,000	23,097,000
Transfers from allowance for loan and lease losses	368,000	970,000
Balance, end of period	25,205,000	24,067,000
Commercial (includes lease financing)
Allowance for Loan and Lease Losses
Beginning Balance	104,156,000	82,965,000
Provision for credit losses, net of transfers	6,068,000	(4,161,000)
Charge-offs	(1,362,000)	(8,917,000)
Recoveries	3,535,000	14,200,000
Net (charge-offs) recoveries	2,173,000	5,283,000
Ending Balance	112,397,000	84,087,000
Allowance individually evaluated for impairment	869,000	3,335,000
Allowance collectively evaluated for impairment	111,528,000	80,752,000
Loans and leases, excluding covered loans	7,170,370,000	5,573,782,000
Loans and leases, individually evaluated for impairment	26,639,000	40,415,000
Loans and leases, collectively evaluated for impairment	7,143,731,000	5,533,367,000
Commercial real estate mortgages
Allowance for Loan and Lease Losses
Beginning Balance	48,240,000	45,967,000
Provision for credit losses, net of transfers	4,251,000	1,285,000
Charge-offs	(45,000)	(692,000)
Recoveries	48,000	26,000
Net (charge-offs) recoveries	3,000	(666,000)
Ending Balance	52,494,000	46,586,000
Allowance individually evaluated for impairment	1,148,000	1,019,000
Allowance collectively evaluated for impairment	51,346,000	45,567,000
Loans and leases, excluding covered loans	2,937,457,000	2,213,114,000	2,829,694,000
Loans and leases, individually evaluated for impairment	42,747,000	22,306,000
Loans and leases, collectively evaluated for impairment	2,894,710,000	2,190,808,000
Residential mortgage
Allowance for Loan and Lease Losses
Beginning Balance	10,499,000	14,029,000
Provision for credit losses, net of transfers	(3,201,000)	268,000
Charge-offs	(105,000)	(554,000)
Recoveries	37,000	60,000
Net (charge-offs) recoveries	(68,000)	(494,000)
Ending Balance	7,230,000	13,803,000
Allowance individually evaluated for impairment		331,000
Allowance collectively evaluated for impairment	7,230,000	13,472,000
Loans and leases, excluding covered loans	4,027,741,000	3,805,807,000	3,962,205,000
Loans and leases, individually evaluated for impairment	7,963,000	13,000,000
Loans and leases, collectively evaluated for impairment	4,019,778,000	3,792,807,000
Real estate construction
Allowance for Loan and Lease Losses
Beginning Balance	13,130,000	23,347,000
Provision for credit losses, net of transfers	(5,920,000)	(1,355,000)
Charge-offs		(1,601,000)
Recoveries	2,666,000	1,705,000
Net (charge-offs) recoveries	2,666,000	104,000
Ending Balance	9,876,000	22,096,000
Allowance individually evaluated for impairment	867,000	9,395,000
Allowance collectively evaluated for impairment	9,009,000	12,701,000
Loans and leases, excluding covered loans	247,114,000	313,409,000	222,780,000
Loans and leases, individually evaluated for impairment	44,346,000	67,686,000
Loans and leases, collectively evaluated for impairment	202,768,000	245,723,000
Home Equity Loans and Lines of Credit
Allowance for Loan and Lease Losses
Beginning Balance	7,243,000	8,024,000
Provision for credit losses, net of transfers	(2,303,000)	162,000
Charge-offs	(240,000)	(189,000)
Recoveries	128,000	35,000
Net (charge-offs) recoveries	(112,000)	(154,000)
Ending Balance	4,828,000	8,032,000
Allowance individually evaluated for impairment		38,000
Allowance collectively evaluated for impairment	4,828,000	7,994,000
Loans and leases, excluding covered loans	696,679,000	715,997,000	711,750,000
Loans and leases, individually evaluated for impairment	2,140,000	6,980,000
Loans and leases, collectively evaluated for impairment	694,539,000	709,017,000
Installment loan
Allowance for Loan and Lease Losses
Beginning Balance	1,847,000	1,959,000
Provision for credit losses, net of transfers	(771,000)	(438,000)
Charge-offs	(271,000)	(209,000)
Recoveries	417,000	626,000
Net (charge-offs) recoveries	146,000	417,000
Ending Balance	1,222,000	1,938,000
Allowance collectively evaluated for impairment	1,222,000	1,938,000
Loans and leases, excluding covered loans	137,545,000	125,793,000	142,793,000
Loans and leases, individually evaluated for impairment		550,000
Loans and leases, collectively evaluated for impairment	137,545,000	125,243,000
Unallocated
Allowance for Loan and Lease Losses
Beginning Balance	92,773,000	86,266,000
Provision for credit losses, net of transfers	1,508,000	3,269,000
Ending Balance	94,281,000	89,535,000
Allowance collectively evaluated for impairment	$ 94,281,000	$ 89,535,000