Investments Contractual Maturities of Available-for-Sale Fixed Maturity Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Amortized Cost
Due in one year or less, Amortized Cost	$ 33,012
Due after one year through five years, Amortized Cost	47,430
Due after five years through ten years, Amortized Cost	38,633
Due after ten years, Amortized Cost	134,229
Total fixed maturities, Amortized Cost	465,744	$ 422,255
Estimated Fair Value
Due in one year or less, Estimated Fair Value	32,899
Due after one year through five years, Estimated Fair Value	47,494
Due after five years through ten years, Estimated Fair Value	39,111
Due after ten years, Estimated Fair Value	133,481
Total fixed maturities, Estimated Fair Value	462,534	$ 425,191
Asset-backed securities [Member]
Amortized Cost
Without single maturity date, Amortized Cost	123,397
Estimated Fair Value
Without single maturity date, Estimated Fair Value	122,937
Residential mortgage-backed securities [Member]
Amortized Cost
Without single maturity date, Amortized Cost	89,043
Estimated Fair Value
Without single maturity date, Estimated Fair Value	$ 86,612