Short-Term Borrowings (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Short-term Debt [Line Items]
Short-term borrowings	$ 603,487	$ 594,733
Federal Home Loan Bank Advances, Current Borrowing Capacity	4,840,000	5,570,000
Repurchase Agreements [Member]
Short-term Debt [Line Items]
Short-term borrowings	590,772	592,182
Federal Home Loan Bank Advances [Member]
Short-term Debt [Line Items]
Short-term borrowings	10,000	0
Federal Funds Purchased [Member]
Short-term Debt [Line Items]
Short-term borrowings	2,551	2,551
Unsecured Debt [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	715,000
Unamortized Purchase Accounting Adjustments [Member]
Short-term Debt [Line Items]
Short-term borrowings	$ 164	$ 0