Summary of Investments (Maturities) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Available-For-Sale, Amortized Cost
Due in one year or less	$ 29,859
Due after one year through five years	482,121
Due after five years through 10 years	374,037
Due after 10 years	545,644
Amortized Cost	1,742,282	$ 1,720,291
Available-For-Sale, Fair Value
Due in one year or less	30,220
Due after one year through five years	506,835
Due after five years through 10 years	393,314
Due after 10 years	571,323
Fair Value	1,816,765	1,825,438
Asset-backed securities
Available-For-Sale, Amortized Cost
Securities not categorized by contractual maturity	317
Amortized Cost	317	314
Available-For-Sale, Fair Value
Securities not categorized by contractual maturity	848
Mortgage-backed securities
Available-For-Sale, Amortized Cost
Securities not categorized by contractual maturity	26,092
Amortized Cost	26,092	$ 20,305
Available-For-Sale, Fair Value
Securities not categorized by contractual maturity	26,300
Collateralized mortgage obligations
Available-For-Sale, Amortized Cost
Securities not categorized by contractual maturity	283,411
Available-For-Sale, Fair Value
Securities not categorized by contractual maturity	288,099
Fixed maturities
Available-For-Sale, Amortized Cost
Amortized Cost	1,741,481
Available-For-Sale, Fair Value
Fair Value	$ 1,816,939

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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