Summary of Investments - Maturities (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Amortized Cost
Due in one year or less	$ 84,646
Due after one year through five years	518,815
Due after five years through 10 years	530,822
Due after 10 years	327,424
Amortized Cost	1,794,325	$ 1,662,680
Fair Value
Due in one year or less	84,052
Due after one year through five years	496,253
Due after five years through 10 years	476,969
Due after 10 years	292,056
Fair Value	1,638,512	1,551,336
Asset-backed securities
Amortized Cost
Securities not categorized by contractual maturity	3,575
Amortized Cost	3,575	3,932
Fair Value
Securities not categorized by contractual maturity	3,894
Fair Value	3,894	4,253
Mortgage-backed securities
Amortized Cost
Securities not categorized by contractual maturity	24,470
Amortized Cost	24,470	20,450
Fair Value
Securities not categorized by contractual maturity	21,007
Fair Value	21,007	$ 17,700
Collateralized mortgage obligations
Amortized Cost
Securities not categorized by contractual maturity	304,573
Fair Value
Securities not categorized by contractual maturity	264,407
Fixed maturities
Amortized Cost
Amortized Cost	1,794,325
Fair Value
Fair Value	$ 1,638,638

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