Short-term Borrowings (Narrative) (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Short-term Debt [Line Items]
Short term borrowings	$ 34,611,000
Current borrowing available	436,821,000
Federal Funds Purchased [Member]
Short-term Debt [Line Items]
Short term borrowings	$ 34,611,000	$ 0
Short-term debt, weighted average interest rate	1.54%
Other Correspondent Banks [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	$ 15,000,000