Fair Value Measurements (Details 4) (USD $)	Jun. 30, 2012	Dec. 31, 2011
Financial Assets:
Cash and due from banks	$ 162,893,000	$ 168,376,000
Due from banks - interest-bearing	106,109,000	76,438,000
Federal funds sold	162,000,000
Loans and leases, net of allowance	13,237,675,000	12,046,828,000
Covered loans, net of allowance	1,216,988,000	1,417,289,000
FDIC indemnification asset	170,654,000	204,259,000
Investment in FHLB and FRB stock	99,700,000	107,400,000
Carrying Amount
Financial Assets:
Cash and due from banks	162,900,000	168,400,000
Due from banks - interest-bearing	106,100,000	76,400,000
Federal funds sold	162,000,000
Securities available-for-sale	6,865,900,000	7,571,900,000
Securities held-to-maturity	1,100,200,000	467,700,000
Trading securities	62,600,000	62,000,000
Loans and leases, net of allowance	13,237,700,000	12,046,800,000
Covered loans, net of allowance	1,217,000,000	1,417,300,000
FDIC indemnification asset	170,700,000	204,300,000
Investment in FHLB and FRB stock	99,700,000	107,400,000
Derivative Assets	66,700,000	62,200,000
Financial Liabilities:
Deposits	21,109,100,000	20,387,600,000
Federal funds purchased and securities sold under repurchase agreements	110,000,000	50,000,000
Other short-term borrowings	212,100,000
Long-term debt	712,300,000	697,800,000
Derivative Liabilities	61,400,000	52,900,000
FDIC clawback liability	9,200,000	8,100,000
Fair Value | Quoted Prices in Active Markets Level 1
Financial Assets:
Cash and due from banks	162,900,000	168,400,000
Due from banks - interest-bearing	106,100,000	76,400,000
Federal funds sold	162,000,000
Securities available-for-sale	6,865,900,000	7,571,900,000
Trading securities	62,600,000	62,000,000
Derivative Assets	66,700,000	62,200,000
Financial Liabilities:
Federal funds purchased and securities sold under repurchase agreements	110,000,000	50,000,000
Derivative Liabilities	61,400,000	52,900,000
Fair Value | Significant Other Observable Inputs Level 2
Financial Assets:
Securities available-for-sale	6,865,900,000	7,571,900,000
Securities held-to-maturity	1,127,100,000	473,900,000
Trading securities	62,600,000	62,000,000
Investment in FHLB and FRB stock	99,700,000	107,400,000
Derivative Assets	66,700,000	62,200,000
Financial Liabilities:
Deposits	21,112,900,000	20,392,300,000
Other short-term borrowings	216,000,000
Long-term debt	758,200,000	718,700,000
Derivative Liabilities	61,400,000	52,900,000
Fair Value | Significant Unobservable Inputs Level 3
Financial Assets:
Securities available-for-sale	6,865,900,000	7,571,900,000
Loans and leases, net of allowance	13,694,600,000	12,400,500,000
Covered loans, net of allowance	1,282,200,000	1,472,600,000
FDIC indemnification asset	149,400,000	184,300,000
Financial Liabilities:
Deposits	21,112,900,000	20,392,300,000
Other short-term borrowings	216,000,000
Long-term debt	758,200,000	718,700,000
FDIC clawback liability	$ 9,200,000	$ 8,100,000