Loans, Allowance for Loan and Lease Losses, and Reserve for Off-Balance Sheet Credit Commitments (Details 6) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	$ 12,309,385,000	$ 11,386,628,000
Covered Loans Allowance
Balance, beginning of period	67,389,000
Provision for losses	43,646,000	76,218,000
Charge-offs	(325,000)	(414,000)
Reduction in allowance due to loan removals	(46,145,000)	(8,415,000)
Balance, end of period	64,565,000	67,389,000
Acquired covered loans on nonaccrual status	400,000	2,600,000
Covered loans 30 to 89 days delinquent	49,100,000	99,500,000
Covered loans 90 days or more past due on accrual status	330,200,000	399,000,000
Commercial
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	4,846,594,000	4,136,874,000
Commercial real estate mortgages
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	2,110,749,000	1,958,317,000
Residential mortgage
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	3,763,218,000	3,552,312,000
Fixed
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	1,581,796,000	1,643,046,000
Variable
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	2,181,422,000	1,909,266,000
Real estate construction
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	315,609,000	467,785,000
Construction
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	217,861,000	326,518,000
Land
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	97,748,000	141,267,000
Equity lines of credit
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	741,081,000	733,741,000
Installment loan
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	132,647,000	160,144,000
Commercial Installment loan
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	605,000	31,161,000
Consumer Installment loan
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	132,042,000	128,983,000
Lease financing
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	399,487,000	377,455,000
Nonclassified
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	11,834,998,000	10,653,101,000
Nonclassified | Commercial
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	4,732,663,000	4,009,923,000
Nonclassified | Commercial real estate mortgages
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	1,930,001,000	1,727,353,000
Nonclassified | Residential mortgage
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	3,728,878,000	3,496,540,000
Nonclassified | Fixed
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	1,565,420,000	1,615,970,000
Nonclassified | Variable
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	2,163,458,000	1,880,570,000
Nonclassified | Real estate construction
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	191,633,000	183,071,000
Nonclassified | Construction
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	147,916,000	129,671,000
Nonclassified | Land
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	43,717,000	53,400,000
Nonclassified | Equity lines of credit
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	724,045,000	716,276,000
Nonclassified | Installment loan
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	131,522,000	148,254,000
Nonclassified | Commercial Installment loan
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	601,000	21,349,000
Nonclassified | Consumer Installment loan
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	130,921,000	126,905,000
Nonclassified | Lease financing
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	396,256,000	371,684,000
Classified
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	474,387,000	733,527,000
Classified | Commercial
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	113,931,000	126,951,000
Classified | Commercial real estate mortgages
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	180,748,000	230,964,000
Classified | Residential mortgage
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	34,340,000	55,772,000
Classified | Fixed
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	16,376,000	27,076,000
Classified | Variable
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	17,964,000	28,696,000
Classified | Real estate construction
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	123,976,000	284,714,000
Classified | Construction
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	69,945,000	196,847,000
Classified | Land
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	54,031,000	87,867,000
Classified | Equity lines of credit
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	17,036,000	17,465,000
Classified | Installment loan
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	1,125,000	11,890,000
Classified | Commercial Installment loan
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	4,000	9,812,000
Classified | Consumer Installment loan
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	1,121,000	2,078,000
Classified | Lease financing
Financing Receivable, Recorded Investment
Loans and leases, excluding covered loans	$ 3,231,000	$ 5,771,000