Investments - Contractual Maturities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
AFS fixed maturities, Amortized cost
Due in one year or less	$ 124,415
Due after one year through five years	527,356
Due after five years through ten years	195,916
Total before securities without single maturities, Amortized cost	847,687
Original or amortized cost	1,530,689	$ 1,813,426
AFS fixed maturities, Fair value
Due in one year or less	123,759
Due after one year through five years	508,288
Due after five years through ten years	188,337
Total before securities without single maturities, Fair value	820,384
Total AFS fixed maturities, Fair value	1,508,544	1,835,518
U.S. agency bonds – mortgage-backed
AFS fixed maturities, Amortized cost
Amortized cost of securities without single maturities	495,747
Original or amortized cost	495,747	533,296
AFS fixed maturities, Fair value
Fair value of securities without single maturities	515,125
Total AFS fixed maturities, Fair value	515,125	538,722
Asset-backed securities
AFS fixed maturities, Amortized cost
Amortized cost of securities without single maturities	187,255
Original or amortized cost	187,255	187,881
AFS fixed maturities, Fair value
Fair value of securities without single maturities	173,035
Total AFS fixed maturities, Fair value	$ 173,035	$ 188,170