Summary of Significant Accounting Policies - Schedule of Effects of Reclassifications out of Accumulated Other Comprehensive Earnings (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Reclassification Adjustment Out of Accumulated Other Comprehensive Income
Net realized gains	$ 14,150	$ 15,152
Earnings (loss) before income taxes	89,834	(79,364)
Income tax benefit (expense)	(16,822)	18,097
Net earnings (loss)	73,012	(61,267)
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	1,183	2,306
Credit losses on available-for-sale securities	22	(849)
Earnings (loss) before income taxes	1,205	1,457
Income tax benefit (expense)	(253)	(306)
Net earnings (loss)	$ 952	$ 1,151