Summary of Significant Accounting Policies - Effects of Reclassifications out of Accumulated Other Comprehensive Earnings (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss)
Earnings (loss) before income taxes	$ 103,303		$ 96,031		$ 263,294	$ 218,822
Income tax (expense) benefit	(21,311)		(18,379)		(53,402)	(42,359)
Net earnings (loss)	81,992	$ 127,900	77,652	$ 98,811	209,892	176,463
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	(931)		(824)		(1,765)	(2,536)
Credit gains (losses) presented within net realized gains	9		31		79	(95)
Earnings (loss) before income taxes	(922)		(793)		(1,686)	(2,631)
Income tax (expense) benefit	194		167		354	553
Net earnings (loss)	$ (728)		$ (626)		$ (1,332)	$ (2,078)