Investments - Fixed-maturity Securities Classified by Contractual Maturity Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Available-for-sale Securities, Debt Maturities [Abstract]
Available-for-sale debt securities, at fair value	$ 2,719,467	$ 2,495,456
Fixed Maturities
Available-for-sale Securities, Debt Maturities [Abstract]
Due in one year or less, amortized cost	209,201
Due after one year through five years, amortized cost	706,348
Due after five years through 10 years, amortized cost	809,733
Due after 10 years, amortized cost	323,848
Total fixed-maturity securities with single maturity dates, amortized cost	2,049,130
Mortgage and asset-backed securities, amortized cost	886,082
Available-for-sale debt securities, amortized cost basis	2,935,212	$ 2,801,415
Due in one year or less, fair value	206,639
Due after one year through five years, fair value	681,350
Due after five years through 10 years, fair value	739,504
Due after 10 years, fair value	294,918
Total fixed-maturity securities with single maturity dates, fair value	1,922,411
Mortgage and asset-backed securities, fair value	797,056
Available-for-sale debt securities, at fair value	$ 2,719,467