Investments (Amortized Cost and Fair Value of Fixed Maturities by Contractual Maturities) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Amortized Cost:
Due in one year or less	$ 48,076
Due after one year through five years	206,128
Due after five years through ten years	207,481
Due after ten years	959,976
Amortized Cost	1,587,004	$ 1,437,796
Fair value:
Due in one year or less	48,656
Due after one year through five years	213,023
Due after five years through ten years	216,827
Due after ten years	1,114,954
Fair Value	1,771,553	1,550,096
Asset-backed securities
Amortized Cost:
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost	18,020
Fair value:
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value	18,437
Commercial mortgage-backed securities
Amortized Cost:
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost	143,676
Fair value:
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value	155,374
Residential mortgage-backed securities
Amortized Cost:
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost	3,647
Fair value:
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value	4,282
Fixed maturities
Amortized Cost:
Amortized Cost	1,587,004	1,437,796
Fair value:
Fair Value	1,771,553	1,550,096
Fixed maturities \| Asset-backed securities
Amortized Cost:
Amortized Cost	18,020	17,816
Fair value:
Fair Value	18,437	18,542
Fixed maturities \| Commercial mortgage-backed securities
Amortized Cost:
Amortized Cost	143,676	141,593
Fair value:
Fair Value	155,374	147,389
Fixed maturities \| Residential mortgage-backed securities
Amortized Cost:
Amortized Cost	3,647	4,068
Fair value:
Fair Value	$ 4,282	$ 4,573

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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