Federal Income Taxes - Schedule of Total Federal Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Taxes (benefits) on earnings from continuing operations:
Current	$ (275)	$ 58,834	$ (1,697)
Deferred	20,031	(25,294)	26,446
Taxes on earnings from continuing operations	19,756	33,540	24,749
Taxes (benefits) on components of stockholders' equity	89,135	25,817	(12,462)
Total Federal income taxes	108,084	59,357	12,242
Net unrealized gains and losses on securities available-for-sale
Taxes (benefits) on earnings from continuing operations:
Taxes (benefits) on components of stockholders' equity	92,528	26,836	(15,870)
Foreign currency translation adjustments
Taxes (benefits) on earnings from continuing operations:
Taxes (benefits) on components of stockholders' equity	4	139	360
Change in benefit plan liability
Taxes (benefits) on earnings from continuing operations:
Taxes (benefits) on components of stockholders' equity	(3,398)	(1,158)	3,003
Change in accounting
Taxes (benefits) on earnings from continuing operations:
Taxes (benefits) on components of stockholders' equity	$ (806)	$ 0	$ 0