Investments - Schedule of Contract Maturities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Cost or Amortized Cost
One year or less	$ 103,318
After one year through five years	472,778
After five years through ten years	293,830
After ten years	206,874
Residential mortgage-backed	282,396
Commercial mortgage and asset-backed	303,161
Redeemable preferred stock	2,025
Total fixed maturity securities, Cost or Amortized Cost	1,664,382
Fair Value
One year or less	104,395
After one year through five years	498,541
After five years through ten years	316,790
After ten years	223,318
Residential mortgage-backed	291,188
Commercial mortgage and asset-backed	311,181
Redeemable preferred stock	1,991
Total investments available-for-sale, Fair Value	$ 1,747,404	$ 1,433,626