Fair Value Measurements (Details 5) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Financial Assets:
Cash and due from banks	$ 151,969,000	$ 168,376,000
Due from banks - interest-bearing	246,336,000	76,438,000
Federal funds sold	17,100,000
Loans and leases, net of allowance	14,540,407,000	12,046,828,000
Covered loans, net of allowance	986,223,000	1,417,289,000
FDIC indemnification asset	150,018,000	204,259,000
Investment in FHLB and FRB stock	90,000,000	107,400,000
Quoted Prices in Active Markets Level 1
Financial Assets:
Cash and due from banks	152,000,000	168,400,000
Due from banks - interest-bearing	246,300,000	76,400,000
Federal funds sold	17,100,000
Financial Liabilities:
Federal funds purchased and securities sold under repurchase agreements	1,214,200,000	50,000,000
Significant Other Observable Inputs Level 2
Financial Assets:
Securities held-to-maturity	1,446,600,000	473,900,000
Loans and leases, net of allowance	4,500,000	24,900,000
Investment in FHLB and FRB stock	90,000,000	107,400,000
Financial Liabilities:
Deposits	22,734,500,000	19,476,200,000
Other short-term borrowings	207,600,000
Long-term debt	698,900,000	718,700,000
Significant Unobservable Inputs Level 3
Financial Assets:
Loans and leases, net of allowance	14,984,100,000	12,375,600,000
Covered loans, net of allowance	1,055,000,000	1,472,600,000
FDIC indemnification asset	123,900,000	184,300,000
Financial Liabilities:
Deposits	772,400,000	916,100,000
Other short-term borrowings	3,100,000
Long-term debt	75,900,000
Carrying Amount
Financial Assets:
Cash and due from banks	152,000,000	168,400,000
Due from banks - interest-bearing	246,300,000	76,400,000
Federal funds sold	17,100,000
Securities held-to-maturity	1,398,400,000	467,700,000
Loans and leases, net of allowance	14,540,400,000	12,046,800,000
Covered loans, net of allowance	986,200,000	1,417,300,000
FDIC indemnification asset	150,000,000	204,300,000
Investment in FHLB and FRB stock	90,000,000	107,400,000
Financial Liabilities:
Deposits	23,502,400,000	20,387,600,000
Federal funds purchased and securities sold under repurchase agreements	1,214,200,000	50,000,000
Other short-term borrowings	209,600,000
Long-term debt	706,100,000	697,800,000
Fair Value
Financial Assets:
Cash and due from banks	152,000,000	168,400,000
Due from banks - interest-bearing	246,300,000	76,400,000
Federal funds sold	17,100,000
Securities held-to-maturity	1,446,600,000	473,900,000
Loans and leases, net of allowance	14,988,600,000	12,400,500,000
Covered loans, net of allowance	1,055,000,000	1,472,600,000
FDIC indemnification asset	123,900,000	184,300,000
Investment in FHLB and FRB stock	90,000,000	107,400,000
Financial Liabilities:
Deposits	23,506,900,000	20,392,300,000
Federal funds purchased and securities sold under repurchase agreements	1,214,200,000	50,000,000
Other short-term borrowings	210,700,000
Long-term debt	$ 774,800,000	$ 718,700,000