Investments - Schedule of Fixed Maturities by Contractual Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Amortized Cost, net
Due in one year or less	$ 111,956
Due after one year through five years	748,300
Due after five years through ten years	1,841,477
Due after ten years through twenty years	8,954,048
Due after twenty years	7,301,254
Mortgage-backed and asset-backed securities	120,287
Fixed maturities, net of allowance for credit losses	19,077,322
Fair Value
Due in one year or less	111,456
Due after one year through five years	771,458
Due after five years through ten years	1,912,103
Due after ten years through twenty years	8,827,993
Due after twenty years	6,587,150
Mortgage-backed and asset-backed securities	124,410
Fixed maturities, fair value	$ 18,334,570	$ 17,870,206