Fair Value Measurements (Details 5) (USD $)	Jun. 30, 2014	Dec. 31, 2013
Financial Assets:
Cash and due from banks	$ 586,273,000	$ 183,227,000
Due from banks - interest-bearing	554,044,000	552,719,000
Federal funds sold and securities purchased under resale agreements	200,000,000	200,000,000
Securities purchased under resale agreements	200,108,000	200,000,000
Securities held-to-maturity	3,441,984,000	2,883,935,000
Loans and leases, net of allowance	18,163,512,000	16,867,854,000
Covered loans, net of allowance	596,667,000	700,989,000
FDIC indemnification asset	68,038,000	89,227,000
Investment in FHLB and FRB stock	58,400,000	64,400,000
Quoted Prices in Active Markets Level 1
Financial Assets:
Cash and due from banks	586,300,000	183,200,000
Due from banks - interest-bearing	554,000,000	552,700,000
Financial Liabilities:
Federal funds purchased	50,000,000
Significant Other Observable Inputs Level 2
Financial Assets:
Securities purchased under resale agreements	203,700,000	200,500,000
Securities held-to-maturity	3,442,000,000	2,883,900,000
Investment in FHLB and FRB stock	58,400,000	64,400,000
Financial Liabilities:
Deposits	26,038,400,000	24,990,800,000
Other short-term borrowings	105,000,000
Long-term debt	612,200,000	697,800,000
Significant Unobservable Inputs Level 3
Financial Assets:
Loans and leases, net of allowance	18,738,100,000	17,362,900,000
Covered loans, net of allowance	645,900,000	739,500,000
FDIC indemnification asset	54,900,000	74,300,000
Financial Liabilities:
Deposits	615,200,000	691,400,000
Other short-term borrowings	5,300,000	3,900,000
Long-term debt	88,100,000	91,100,000
Carrying Amount
Financial Assets:
Cash and due from banks	586,300,000	183,200,000
Due from banks - interest-bearing	554,000,000	552,700,000
Securities purchased under resale agreements	200,000,000	200,000,000
Securities held-to-maturity	3,418,400,000	2,957,800,000
Loans and leases, net of allowance	18,163,500,000	16,867,900,000
Covered loans, net of allowance	596,700,000	701,000,000
FDIC indemnification asset	68,000,000	89,200,000
Investment in FHLB and FRB stock	58,400,000	64,400,000
Financial Liabilities:
Deposits	26,651,500,000	25,679,400,000
Federal funds purchased	50,000,000
Other short-term borrowings	110,300,000	3,900,000
Long-term debt	627,800,000	736,000,000
Fair Value
Financial Assets:
Cash and due from banks	586,300,000	183,200,000
Due from banks - interest-bearing	554,000,000	552,700,000
Securities purchased under resale agreements	203,700,000	200,500,000
Securities held-to-maturity	3,442,000,000	2,883,900,000
Loans and leases, net of allowance	18,738,100,000	17,362,900,000
Covered loans, net of allowance	645,900,000	739,500,000
FDIC indemnification asset	54,900,000	74,300,000
Investment in FHLB and FRB stock	58,400,000	64,400,000
Financial Liabilities:
Deposits	26,653,600,000	25,682,200,000
Federal funds purchased	50,000,000
Other short-term borrowings	110,300,000	3,900,000
Long-term debt	$ 700,300,000	$ 788,900,000