Short-Term Borrowings (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Short-term Debt [Line Items]
Short-term borrowings	$ 511,418,000	$ 568,505,000
Master Notes [Member]
Short-term Debt [Line Items]
Short-term borrowings	411,907,000	399,047,000
Repurchase Agreements [Member]
Short-term Debt [Line Items]
Short-term borrowings	96,960,000	111,907,000
Federal Home Loan Bank Advances [Member]
Short-term Debt [Line Items]
Short-term borrowings	0	55,000,000
Federal Funds Purchased [Member]
Short-term Debt [Line Items]
Short-term borrowings	2,551,000	2,551,000
Unsecured Debt [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	665,000,000
Secured Debt [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	$ 1,140,000,000