Investments (Amortized Cost and Aggregate Fair Value of Debt Securities, by Contractual Maturity) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Investments [Abstract]
Available-for-sale Securities, Due in one year or less, Amortized Cost	$ 1,093
Available-for-sale Securities, Due in one year or less, Fair Value	1,100
Available-for-sale Securities, Due after one year through five years, Amortized Cost	17,858
Available-for-sale Securities, Due after one year through five years, Fair Value	17,806
Available-for-sale Securities, Due after five years through ten years, Amortized Cost	27,667
Available-for-sale Securities, Due after five years through ten years, Fair Value	27,317
Available-for-sale Securities, Due after ten years, Amortized Cost	51,896
Available-for-sale Securities, Due after ten years, Fair Value	50,813
Available-for-sale securities, Amortized Cost	98,514	$ 94,467
Available-for-sale Securities, Fair Value	97,036
Held-to-maturity Securities, Due in one year or less, Amortized Cost	0
Held-to-maturity Securities, Due in one year or less, Fair Value	0
Held-to-maturity Securities, Due after one year through five years, Amortized Cost	4
Held-to-maturity Securities, Due after one year through five years, Fair Value	5
Held-to-maturity Securities, Due after five years through ten years, Amortized Cost	48
Held-to-maturity Securities, Due after five years through ten years, Fair Value	50
Held-to-maturity Securities, Due after ten years, Amortized Cost	1,471
Held-to-maturity Securities, Due after ten years, Fair Value	1,457
Held-to-maturity Securities, Amortized Cost	1,523	1,616
Held-to-maturity Securities, Fair Value	$ 1,512	$ 1,645