Investments Contractual Maturities of Available-for-Sale Fixed Maturity Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Amortized Cost
Due in one year or less, Amortized Cost	$ 24,944
Due after one year through five years, Amortized Cost	49,867
Due after five years through ten years, Amortized Cost	39,180
Due after ten years, Amortized Cost	128,088
Total fixed maturities, Amortized Cost	472,418	$ 422,255
Estimated Fair Value
Due in one year or less, Estimated Fair Value	24,857
Due after one year through five years, Estimated Fair Value	49,735
Due after five years through ten years, Estimated Fair Value	39,529
Due after ten years, Estimated Fair Value	127,095
Total fixed maturities, Estimated Fair Value	467,922	$ 425,191
Asset-backed securities [Member]
Amortized Cost
Without single maturity date, Amortized Cost	125,030
Estimated Fair Value
Without single maturity date, Estimated Fair Value	124,048
Residential mortgage-backed securities [Member]
Amortized Cost
Without single maturity date, Amortized Cost	105,309
Estimated Fair Value
Without single maturity date, Estimated Fair Value	$ 102,658