Summary of Significant Accounting Policies - Effects of Reclassifications out of Accumulated Other Comprehensive Earnings (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss)
Net realized gains (losses) - Available-for-sale	$ (3,641)	$ (2,997)	$ 1,859
Earnings before income taxes	377,265	720,678	344,321
Income tax (expense) benefit	(72,654)	(137,267)	(64,967)
Net earnings	304,611	583,411	279,354
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	(3,641)	(2,997)	1,859
Credit gains (losses) presented within net realized gains	32	102	(44)
Earnings before income taxes	(3,609)	(2,895)	1,815
Income tax (expense) benefit	758	608	(381)
Net earnings	$ (2,851)	$ (2,287)	$ 1,434