Investments - Schedule of Contract Maturities (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Cost or Amortized Cost
One year or less	$ 40,895
After one year through five years	317,761
After five years through ten years	193,545
After ten years	117,692
Residential mortgage-backed	190,574
Commercial mortgage and asset-backed	177,286
Redeemable preferred stock	2,025
Total fixed maturity securities, Cost or Amortized Cost	1,039,778	$ 1,008,662
Fair Value
One year or less	40,760
After one year through five years	312,999
After five years through ten years	187,368
After ten years	119,077
Residential mortgage-backed	184,751
Commercial mortgage and asset-backed	174,442
Redeemable preferred stock	1,990
Total investments available-for-sale, Fair Value	$ 1,021,387	$ 1,016,098