Investments - Schedule of Contractual Maturities of Fixed Maturity Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2026	Dec. 31, 2025
Amortized Cost
Amortized Cost	$ 3,691,050	$ 3,410,992
Fair Value
Fair Value	3,581,971	3,439,002
Total fixed maturities
Amortized Cost
Amortized Cost	3,267,687	3,210,940
Fair Value
Fair Value	3,157,925	$ 3,238,543
Fixed Maturities, Excluding Mortgage-backed and Asset-backed Securities
Amortized Cost
Due less than one year	47,870
Due after one through five years	1,418,639
Due after five through ten years	814,853
Due after ten years	81,096
Fair Value
Due less than one year	47,814
Due after one through five years	1,384,030
Due after five through ten years	774,640
Due after ten years	75,187
Mortgage-backed securities
Amortized Cost
Mortgage/Asset-backed	553,693
Fair Value
Mortgage/Asset-backed	527,293
Asset-backed securities
Amortized Cost
Mortgage/Asset-backed	351,536
Fair Value
Mortgage/Asset-backed	$ 348,961

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