Summary of Investments - Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Available-For-Sale, Amortized Cost
Due in one year or less	$ 63,120
Due after one year through five years	475,467
Due after five years through 10 years	386,274
Due after 10 years	427,411
Amortized Cost	1,656,797	$ 1,720,291
Available-For-Sale, Fair Value
Due in one year or less	63,776
Due after one year through five years	496,231
Due after five years through 10 years	403,830
Due after 10 years	450,959
Fair Value	1,719,790	1,825,438
Asset-backed securities
Available-For-Sale, Amortized Cost
Securities not categorized by contractual maturity	325
Amortized Cost	325	314
Available-For-Sale, Fair Value
Securities not categorized by contractual maturity	925
Fair Value	925	926
Mortgage-backed securities
Available-For-Sale, Amortized Cost
Securities not categorized by contractual maturity	25,075
Amortized Cost	25,075	20,305
Available-For-Sale, Fair Value
Securities not categorized by contractual maturity	25,013
Fair Value	25,013	$ 20,577
Collateralized mortgage obligations
Available-For-Sale, Amortized Cost
Securities not categorized by contractual maturity	279,125
Available-For-Sale, Fair Value
Securities not categorized by contractual maturity	279,056
Fixed Maturities
Available-For-Sale, Amortized Cost
Amortized Cost	1,656,797
Available-For-Sale, Fair Value
Fair Value	$ 1,719,790

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in sixth through tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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