Summary of Significant Accounting Policies - Schedule of Unrealized Gains and Losses on Available-for-Sale Securities Reclassified out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other net investment gains	$ 14,950	$ 21,071	$ 14,088
Earnings (loss) before Federal income taxes	227,257	112,068	165,156
Federal income taxes (benefit)	46,576	19,756	33,540
Net earnings (loss)	180,681	92,312	131,616
Accumulated Other Comprehensive Income | Amount Reclassified from Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other net investment gains	16,372	5,677	2,787
Net OTTI losses recognized in earnings	0	0	(7,847)
Earnings (loss) before Federal income taxes	16,372	5,677	(5,060)
Federal income taxes (benefit)	3,438	1,192	(1,063)
Net earnings (loss)	$ 12,934	$ 4,485	$ (3,997)