Other Assets - Components of Other Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Other Assets [Abstract]
Prepaid federal income taxes (Note 10)	$ 354,123	$ 354,123
Prepaid reinsurance premiums	181,410	201,674
Company-owned life insurance	106,165	113,386
Loaned securities (Note 5)	95,286	103,996
Right-of-use assets (Note 13)	29,957	31,878
Other	36,824	32,246
Total other assets	$ 803,765	$ 837,303