Investments (Amortized Cost and Aggregate Fair Value of Debt Securities, by Contractual Maturity) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Investments [Abstract]
Available-for-sale Securities, Due in one year or less, Amortized Cost	$ 1,076
Available-for-sale Securities, Due in one year or less, Fair Value	1,075
Available-for-sale Securities, Due after one year through five years, Amortized Cost	17,789
Available-for-sale Securities, Due after one year through five years, Fair Value	18,171
Available-for-sale Securities, Due after five years through ten years, Amortized Cost	29,280
Available-for-sale Securities, Due after five years through ten years, Fair Value	29,832
Available-for-sale Securities, Due after ten years, Amortized Cost	46,322
Available-for-sale Securities, Due after ten years, Fair Value	46,680
Available-for-sale securities, Amortized Cost	94,467	$ 92,837
Available-for-sale Securities, Fair Value	95,758
Held-to-maturity Securities, Due in one year or less, Amortized Cost	2
Held-to-maturity Securities, Due in one year or less, Fair Value	2
Held-to-maturity Securities, Due after one year through five years, Amortized Cost	0
Held-to-maturity Securities, Due after one year through five years, Fair Value	0
Held-to-maturity Securities, Due after five years through ten years, Amortized Cost	60
Held-to-maturity Securities, Due after five years through ten years, Fair Value	65
Held-to-maturity Securities, Due after ten years, Amortized Cost	1,554
Held-to-maturity Securities, Due after ten years, Fair Value	1,578
Held-to-maturity Securities, Amortized Cost	1,616	1,890
Held-to-maturity Securities, Fair Value	$ 1,645	$ 1,930