Basis of Presentation and Summary of Significant Accounting Policies - Effects of Reclassifications out of Accumulated Other Comprehensive Earnings (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss)
Earnings (loss) before income taxes	$ 116,825			$ 15,019			$ 380,119	$ 233,841
Income tax (expense) benefit	(21,798)			(1,483)			(75,200)	(43,842)
Net earnings (loss)	95,027	$ 81,992	$ 127,900	13,536	$ 77,652	$ 98,811	304,919	189,999
Unrealized Gains and Losses on Available-for-Sale Securities | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss)
Net realized gains (losses) - Available-for-sale	(1,365)			(271)			(3,129)	(2,808)
Credit gains (losses) presented within net realized gains	(6)			(270)			72	(365)
Earnings (loss) before income taxes	(1,371)			(541)			(3,057)	(3,173)
Income tax (expense) benefit	288			114			642	666
Net earnings (loss)	$ (1,083)			$ (427)			$ (2,415)	$ (2,507)