Securities Sold Under Agreements to Repurchase (Repurchase Agreements) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Gross Amounts of Recognized Liabilities	$ 33,435	$ 36,908
Gross Amounts Offset in the Statements of Condition	0	0
Net Amounts of Liabilities Presented in the Statements of Condition	33,435	36,908
Financial Instruments	(33,435)	(36,908)
Cash Collateral Pledged	0	0
Net Amount	0	0
Fair value of securities pledged in connection with repurchase agreements	40,470	$ 42,397
Total	33,435
U.S. Treasury and agency securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total	33,435
Overnight and Continuous
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total	33,435
Overnight and Continuous | U.S. Treasury and agency securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total	33,435
Up to 30 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total	0
Up to 30 Days | U.S. Treasury and agency securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total	0
30 - 90 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total	0
30 - 90 Days | U.S. Treasury and agency securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total	0
Greater than 90 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total	0
Greater than 90 Days | U.S. Treasury and agency securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total	$ 0