Investments Contractual Maturities of Available-for-Sale Fixed Maturity Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Amortized Cost
Due in one year or less, Amortized Cost	$ 4,270
Due after one year through five years, Amortized Cost	75,192
Due after five years through ten years, Amortized Cost	53,708
Due after ten years, Amortized Cost	101,747
Total fixed maturities, Amortized Cost	536,182	$ 514,237
Estimated Fair Value
Due in one year or less, Estimated Fair Value	4,265
Due after one year through five years, Estimated Fair Value	76,142
Due after five years through ten years, Estimated Fair Value	55,609
Due after ten years, Estimated Fair Value	104,379
Estimated Fair Value	540,778	510,251
Commercial mortgage and asset-backed securities [Member]
Amortized Cost
Without single maturity date, Amortized Cost	164,341
Total fixed maturities, Amortized Cost	164,341	151,137
Estimated Fair Value
Without single maturity date, Estimated Fair Value	164,412
Estimated Fair Value	164,412	149,867
Residential mortgage-backed securities [Member]
Amortized Cost
Without single maturity date, Amortized Cost	136,924
Total fixed maturities, Amortized Cost	136,924	110,717
Estimated Fair Value
Without single maturity date, Estimated Fair Value	135,971
Estimated Fair Value	$ 135,971	$ 108,421