Investments - Amortized Cost and Fair Value of Fixed Income Securities (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Amortized Cost
Due in one year or less	$ 99,035
Due after one through five years	679,649
Due after five through ten years	507,803
Due after ten years	157,628
Amortized Cost	1,444,115
Fair Value
Due in one year or less	99,326
Due after one through five years	692,219
Due after five through ten years	523,276
Due after ten years	160,322
Fair Value	1,475,143
Amortized Cost - Structured securities	1,999,403
Fair Value - Structured securities	2,040,682
ABS
Fair Value
Amortized Cost - Structured securities	73,068
Fair Value - Structured securities	73,582
CLO
Fair Value
Amortized Cost - Structured securities	181,704
Fair Value - Structured securities	179,549
CMBS
Fair Value
Amortized Cost - Structured securities	95,810
Fair Value - Structured securities	97,526
RMBS - non-agency
Fair Value
Amortized Cost - Structured securities	62,343
Fair Value - Structured securities	71,610
RMBS - agency
Fair Value
Amortized Cost - Structured securities	142,363
Fair Value - Structured securities	$ 143,272

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