Investments - Amortized Cost and Fair Value of Fixed Maturity Securities (Details) $ in Thousands	Mar. 31, 2020 USD ($)
Amortized Cost
Due in one year or less	$ 103,407
Due after one through five years	659,203
Due after five through ten years	449,535
Due after ten years	248,896
Amortized Cost	1,461,041
Fair Value
Due in one year or less	103,498
Due after one through five years	657,184
Due after five through ten years	445,004
Due after ten years	239,964
Fair Value	1,445,650
Amortized Cost - Structured securities	2,038,469
Fair Value - Structured securities	2,002,420
Government agency securities
Fair Value
Amortized Cost - Structured securities	27,998
Fair Value - Structured securities	28,589
ABS
Fair Value
Amortized Cost - Structured securities	49,205
Fair Value - Structured securities	46,020
CLO
Fair Value
Amortized Cost - Structured securities	177,411
Fair Value - Structured securities	157,563
CMBS
Fair Value
Amortized Cost - Structured securities	94,816
Fair Value - Structured securities	94,474
RMBS - non-agency
Fair Value
Amortized Cost - Structured securities	92,189
Fair Value - Structured securities	90,633
RMBS - agency
Fair Value
Amortized Cost - Structured securities	135,809
Fair Value - Structured securities	$ 139,491

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