Investments - Schedule of Contractual Maturities of Fixed Maturity Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Amortized  Cost
Due in less than one year	$ 587,720	$ 364,501
Due after one through five years	11,439,510	8,117,971
Due after five through ten years	5,182,667	4,072,142
Due after ten years	307,392	356,268
Amortized cost	20,872,450	15,038,551
Debt Securities, Trading, and Equity Securities, FV-NI [Abstract]
Due in less than one year	582,519	356,770
Due after one through five years	11,468,263	7,875,771
Due after five through ten years	5,188,716	3,805,287
Due after ten years	292,473	311,856
Fixed maturity investments trading	20,877,108	14,351,402
Mortgage-backed
Amortized  Cost
Amortized cost	1,864,520	1,009,205
Debt Securities, Trading, and Equity Securities, FV-NI [Abstract]
Fixed maturity investments trading	1,853,442	924,416
Asset-backed
Amortized  Cost
Amortized cost	1,490,641	1,118,464
Debt Securities, Trading, and Equity Securities, FV-NI [Abstract]
Fixed maturity investments trading	$ 1,491,695	$ 1,077,302