Fair Value Measurements (Details 5) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Financial Assets:
Cash and due from banks	$ 301,106,000	$ 151,969,000
Due from banks - interest-bearing	1,045,608,000	246,336,000
Securities purchased under resale agreements	200,000,000
Loans and leases, net of allowance	16,270,186,000	14,540,407,000
Covered loans, net of allowance	754,190,000	986,223,000
FDIC indemnification asset	101,124,000	150,018,000
Investment in FHLB and FRB stock	71,800,000	90,000,000
Quoted Prices in Active Markets Level 1
Financial Assets:
Cash and due from banks	301,100,000	152,000,000
Due from banks - interest-bearing	1,045,600,000	246,300,000
Federal funds sold		17,100,000
Financial Liabilities:
Federal funds purchased and securities sold under repurchase agreements		1,214,200,000
Significant Other Observable Inputs Level 2
Financial Assets:
Securities purchased under resale agreements	197,000,000
Securities held-to-maturity	1,608,100,000	1,446,600,000
Investment in FHLB and FRB stock	71,800,000	90,000,000
Financial Liabilities:
Deposits	24,503,000,000	22,734,500,000
Other short-term borrowings		207,600,000
Long-term debt	693,600,000	698,900,000
Significant Unobservable Inputs Level 3
Financial Assets:
Loans and leases, net of allowance	16,719,800,000	14,988,600,000
Covered loans, net of allowance	802,500,000	1,055,000,000
FDIC indemnification asset	84,300,000	123,900,000
Financial Liabilities:
Deposits	737,000,000	772,400,000
Other short-term borrowings	2,600,000	3,100,000
Long-term debt	84,600,000	75,900,000
Carrying Amount
Financial Assets:
Cash and due from banks	301,100,000	152,000,000
Due from banks - interest-bearing	1,045,600,000	246,300,000
Securities purchased under resale agreements	200,000,000
Federal funds sold		17,100,000
Securities held-to-maturity	1,649,500,000	1,398,400,000
Loans and leases, net of allowance	16,270,200,000	14,540,400,000
Covered loans, net of allowance	754,200,000	986,200,000
FDIC indemnification asset	101,100,000	150,000,000
Investment in FHLB and FRB stock	71,800,000	90,000,000
Financial Liabilities:
Deposits	25,236,900,000	23,502,400,000
Federal funds purchased and securities sold under repurchase agreements		1,214,200,000
Other short-term borrowings	2,600,000	209,600,000
Long-term debt	719,300,000	706,100,000
Fair Value
Financial Assets:
Cash and due from banks	301,100,000	152,000,000
Due from banks - interest-bearing	1,045,600,000	246,300,000
Securities purchased under resale agreements	197,000,000
Federal funds sold		17,100,000
Securities held-to-maturity	1,608,100,000	1,446,600,000
Loans and leases, net of allowance	16,719,800,000	14,988,600,000
Covered loans, net of allowance	802,500,000	1,055,000,000
FDIC indemnification asset	84,300,000	123,900,000
Investment in FHLB and FRB stock	71,800,000	90,000,000
Financial Liabilities:
Deposits	25,240,000,000	23,506,900,000
Federal funds purchased and securities sold under repurchase agreements		1,214,200,000
Other short-term borrowings	2,600,000	210,700,000
Long-term debt	$ 778,200,000	$ 774,800,000