Investments - Schedule of Realized Gain (Loss) on Investments (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Sales and other									$ (77,301)	$ (32,552)	$ 34,916
Provision for credit losses									(7,115)	387	2,959
Fair value option—change in fair value									15,102	(29,353)	22,918
Mortgage loans									(5,603)	(963)	1,788
Other investments									1,792	4,681	(135)
Realized gains (losses) from investments									(73,125)	(57,800)	62,446
Realized loss on redemption of debt									0	0	(9,314)
Other gains (losses)									7,449	(18,748)	6,187
Total realized gains (losses)	$ 13,287	$ (2,193)	$ (45,843)	$ (30,927)	$ (9,703)	$ (29,155)	$ (30,446)	$ (7,244)	(65,676)	(76,548)	59,319
Applicable tax									13,792	16,075	(12,457)
Realized gains (losses), net of tax									(51,884)	(60,473)	46,862
Exchanges of fixed maturities									50,900	147,600	109,200
Exchanges of fixed maturities, net realized gains									(1,900)	$ 1,900	$ 25,200
Securities sold with a provision for credit losses									$ 66,000