Summary of Significant Accounting Policies - Schedule of Effects of Reclassifications out of Accumulated Other Comprehensive Earnings (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Reclassification Adjustment Out of Accumulated Other Comprehensive Income
Net realized gains	$ 64,222	$ 17,885	$ 17,520
Earnings before income taxes	344,321	189,841	232,734
Income tax expense	(64,967)	(32,750)	(41,092)
Net earnings	279,354	157,091	191,642
Unrealized Gains and Losses on Available-for-Sale Securities | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment Out of Accumulated Other Comprehensive Income
Net realized gains	1,859	3,872	3,184
Credit losses presented within net realized gains	(44)	(369)
Earnings before income taxes	1,815	3,503	3,184
Income tax expense	(381)	(736)	(669)
Net earnings	$ 1,434	$ 2,767	$ 2,515