Investments - Investments Classified by Contractual Maturity Date (Details) - Fixed Maturities - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Cost or Amortized Cost
Due in one year or less	$ 69,381
Due after one year through five years	393,536
Due after five years through ten years	234,739
Due after ten years	15,868
Cost or adjusted/amortized cost	$ 713,524	$ 497,616
Percent of Total
Due in one year or less	9.70%
Due after one year through five years	55.20%
Due after five years through ten years	32.90%
Due after ten years	2.20%
Total	100.00%
Fair Value
Due in one year or less	$ 69,331
Due after one year through five years	394,736
Due after five years through ten years	236,103
Due after ten years	16,013
Total	$ 716,183	$ 494,516
Percent of Total
Due in one year or less	9.70%
Due after one year through five years	55.10%
Due after five years through ten years	33.00%
Due after ten years	2.20%
Total	100.00%