Investments (Held-to-Maturity Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 1,616	$ 1,890
Held-to-maturity securities, unrealized gains	29	40
Held-to-maturity securities, unrealized losses	0	0
Fair Value	1,645	1,930
Mortgage backed securities
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	1,615	1,863
Held-to-maturity securities, unrealized gains	29	38
Held-to-maturity securities, unrealized losses	0	0
Fair Value	1,644	1,901
U.S. Treasury securities and obligations of U.S. Government corporations and agencies
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	1	27
Held-to-maturity securities, unrealized gains	0	2
Held-to-maturity securities, unrealized losses	0	0
Fair Value	$ 1	$ 29