Investments - Fixed-maturity Securities Classified by Contractual Maturity Securities (Details) (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Available-for-sale Securities, Debt Maturities [Abstract]
Total available-for-sale fixed-maturity securities	$ 2,796,030	$ 2,719,467
Fixed Maturities
Available-for-sale Securities, Debt Maturities [Abstract]
Due in one year or less, amortized cost	183,824
Due after one year through five years, amortized cost	745,364
Due after five years through 10 years, amortized cost	819,934
Due after 10 years, amortized cost	412,067
Total fixed-maturity securities with single maturity dates, amortized cost	2,161,189
Mortgage and asset-backed securities, amortized cost	872,725
Available-for-sale debt securities, amortized cost basis	3,033,914	$ 2,935,212
Due in one year or less, fair value	182,161
Due after one year through five years, fair value	716,707
Due after five years through 10 years, fair value	741,336
Due after 10 years, fair value	373,495
Total fixed-maturity securities with single maturity dates, fair value	2,013,699
Mortgage and asset-backed securities, fair value	782,331
Total available-for-sale fixed-maturity securities	$ 2,796,030