Investments - Amortized Cost and Fair Value of Fixed Income Securities (Details) $ in Thousands	Sep. 30, 2019 USD ($)
Amortized Cost
Due in one year or less	$ 97,372
Due after one through five years	722,887
Due after five through ten years	514,633
Due after ten years	105,273
Amortized Cost	1,440,165
Fair Value
Due in one year or less	97,585
Due after one through five years	733,382
Due after five through ten years	531,014
Due after ten years	106,754
Fair Value	1,468,735
Amortized Cost - Structured securities	1,985,250
Fair Value - Structured securities	2,025,955
ABS
Fair Value
Amortized Cost - Structured securities	84,227
Fair Value - Structured securities	85,216
CLO
Fair Value
Amortized Cost - Structured securities	181,843
Fair Value - Structured securities	179,744
CMBS
Fair Value
Amortized Cost - Structured securities	67,986
Fair Value - Structured securities	70,360
RMBS - non-agency
Fair Value
Amortized Cost - Structured securities	63,803
Fair Value - Structured securities	74,314
RMBS - agency
Fair Value
Amortized Cost - Structured securities	147,226
Fair Value - Structured securities	$ 147,586

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