Loans, Allowance for Loan and Lease Losses, and Reserve for Off-Balance Sheet Credit Commitments (Details) (USD $)	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011
Accounts notes and loans receivable
Loans and leases, excluding covered loans	$ 15,216,906,000	$ 14,818,295,000	$ 12,747,902,000
Less: Allowance for loan and lease losses	(282,328,000)	(277,888,000)	(266,077,000)	(262,557,000)
Loans and leases, excluding covered loans, net	14,934,578,000	14,540,407,000
Covered loans	951,917,000	1,031,004,000
Less: Allowance for loan losses	(42,354,000)	(44,781,000)	(61,471,000)	(64,565,000)
Covered loans, net	909,563,000	986,223,000	1,438,714,000
Total loans and leases	16,168,823,000	15,849,299,000
Net loans and leases	15,844,141,000	15,526,630,000
Unamortized fees, net of deferred costs	6,200,000	5,900,000
Commercial
Accounts notes and loans receivable
Loans and leases, excluding covered loans	6,452,477,000	6,211,353,000
Covered loans	9,611,000	10,561,000
Commercial real estate mortgages
Accounts notes and loans receivable
Loans and leases, excluding covered loans	2,937,457,000	2,829,694,000	2,213,114,000
Less: Allowance for loan and lease losses	(52,494,000)	(48,240,000)	(46,586,000)	(45,967,000)
Covered loans	863,161,000	931,758,000
Residential mortgage
Accounts notes and loans receivable
Loans and leases, excluding covered loans	4,027,741,000	3,962,205,000	3,805,807,000
Less: Allowance for loan and lease losses	(7,230,000)	(10,499,000)	(13,803,000)	(14,029,000)
Covered loans	5,619,000	5,652,000
Real estate construction
Accounts notes and loans receivable
Loans and leases, excluding covered loans	247,114,000	222,780,000	313,409,000
Less: Allowance for loan and lease losses	(9,876,000)	(13,130,000)	(22,096,000)	(23,347,000)
Covered loans	69,380,000	78,554,000
Home equity loans and lines of credit
Accounts notes and loans receivable
Loans and leases, excluding covered loans	696,679,000	711,750,000	715,997,000
Less: Allowance for loan and lease losses	(4,828,000)	(7,243,000)	(8,032,000)	(8,024,000)
Covered loans	3,499,000	3,790,000
Installment loan
Accounts notes and loans receivable
Loans and leases, excluding covered loans	137,545,000	142,793,000	125,793,000
Less: Allowance for loan and lease losses	(1,222,000)	(1,847,000)	(1,938,000)	(1,959,000)
Covered loans	647,000	689,000
Lease financing
Accounts notes and loans receivable
Loans and leases, excluding covered loans	$ 717,893,000	$ 737,720,000