Schedule II - Condensed Financial Information of Registrant (Balance Sheets (Parent Company)) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Assets:
Cash and cash equivalents	$ 1,363,195	$ 1,449,346
Fixed maturity securities available for sale at fair value (cost $190,708 and $285,900 at December 31, 2023 and 2022, respectively)	20,178,308	17,587,349
Loans receivable (net of allowance for expected credit losses of $1,146 and $559 at December 31, 2023 and 2022, respectively)	201,271	193,002
Current federal income taxes	1,318	39,123
Deferred federal and foreign income taxes	309,623	340,647
Property, furniture and equipment at cost, less accumulated depreciation	426,803	423,232
Other assets	865,556	736,022
Total assets	37,202,015	33,861,099
Liabilities:
Other liabilities	1,503,053	1,377,740
Current federal income taxes	47,525	34,350
Deferred federal income taxes	42,660	11,646
Subordinated debentures	1,009,090	1,008,371
Total liabilities	29,732,778	27,092,938
Stockholders' equity:
Preferred stock	0	0
Common stock	105,803	105,803
Additional paid-in capital	1,017,691	997,534
Retained earnings (including accumulated undistributed net income of subsidiaries of $8,497,674 and $7,975,360 at December 31, 2023 and 2022, respectively)	11,040,908	10,161,005
Accumulated other comprehensive loss	(925,838)	(1,264,581)
Treasury stock, at cost	(3,783,133)	(3,251,429)
Total common stockholders’ equity	7,455,431	6,748,332
Total liabilities and equity	37,202,015	33,861,099
Fixed maturity securities available for sale at cost	20,861,830	18,664,073
Financing receivable, allowance for credit loss	3,004	1,791	$ 1,718
Parent Company
Assets:
Cash and cash equivalents	128,434	103,522
Fixed maturity securities available for sale at fair value (cost $190,708 and $285,900 at December 31, 2023 and 2022, respectively)	189,189	275,511
Loans receivable (net of allowance for expected credit losses of $1,146 and $559 at December 31, 2023 and 2022, respectively)	91,304	109,793
Equity securities, at fair value (cost $3,430 in both 2023 and 2022)	3,430	3,430
Investment in subsidiaries	9,887,117	8,888,455
Current federal income taxes	0	34,452
Deferred federal and foreign income taxes	278,946	304,191
Property, furniture and equipment at cost, less accumulated depreciation	10,382	11,356
Other assets	44,186	39,741
Total assets	10,632,988	9,770,451
Liabilities:
Current federal income taxes	1,721	0
Subordinated debentures	1,009,090	1,008,371
Senior notes	1,821,671	1,821,569
Total liabilities	3,177,557	3,022,119
Stockholders' equity:
Preferred stock		0
Common stock	105,803	105,803
Additional paid-in capital	1,017,691	997,534
Retained earnings (including accumulated undistributed net income of subsidiaries of $8,497,674 and $7,975,360 at December 31, 2023 and 2022, respectively)	11,040,908	10,161,005
Accumulated other comprehensive loss	(925,838)	(1,264,581)
Treasury stock, at cost	(3,783,133)	(3,251,429)
Total common stockholders’ equity	7,455,431	6,748,332
Total liabilities and equity	10,632,988	9,770,451
Fixed maturity securities available for sale at cost	190,708	285,900
Financing receivable, allowance for credit loss	1,146	559
Equity securities available for sale at cost	3,430	3,430
Accumulated undistributed net income of subsidiaries	8,497,674	7,975,360
Parent Company | Related Party
Liabilities:
Other liabilities	178,676	53,029
Parent Company | Nonrelated Party
Liabilities:
Other liabilities	$ 166,399	$ 139,150