Investments (Amortized Cost and Aggregate Fair Value of Debt Securities, by Contractual Maturity) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Investments [Abstract]
Available-for-sale Securities, Due in one year or less, Amortized Cost	$ 1,160
Available-for-sale Securities, Due in one year or less, Fair Value	1,168
Available-for-sale Securities, Due after one year through five years, Amortized Cost	16,753
Available-for-sale Securities, Due after one year through five years, Fair Value	17,015
Available-for-sale Securities, Due after five years through ten years, Amortized Cost	30,876
Available-for-sale Securities, Due after five years through ten years, Fair Value	31,471
Available-for-sale Securities, Due after ten years, Amortized Cost	42,621
Available-for-sale Securities, Due after ten years, Fair Value	43,169
Available-for-sale securities, Amortized Cost	91,410	$ 92,837
Available-for-sale Securities, Fair Value	92,823
Held-to-maturity Securities, Due in one year or less, Amortized Cost	6
Held-to-maturity Securities, Due in one year or less, Fair Value	6
Held-to-maturity Securities, Due after one year through five years, Amortized Cost	1
Held-to-maturity Securities, Due after one year through five years, Fair Value	1
Held-to-maturity Securities, Due after five years through ten years, Amortized Cost	65
Held-to-maturity Securities, Due after five years through ten years, Fair Value	70
Held-to-maturity Securities, Due after ten years, Amortized Cost	1,612
Held-to-maturity Securities, Due after ten years, Fair Value	1,652
Held-to-maturity Securities, Amortized Cost	1,684	1,890
Held-to-maturity Securities, Fair Value	$ 1,729	$ 1,930