Schedule II. Condensed Financial Information of Registrant (Parent Company) (Schedule of Condensed Financial Information of Registrant, Balance Sheets) (Details) - USD ($) $ / shares in Units, $ in Millions	Dec. 31, 2023	Dec. 31, 2022		Dec. 31, 2021	[1]
Assets
Cash	$ 345	$ 475	[1]
Other assets	2,534	2,274	[1]
Total assets	64,711	61,000	[1]
Liabilities
Short-term debt	550	243	[1]
Long-term debt	2,481	2,538	[1]
Other liabilities	2,897	2,983	[1]
Total liabilities	54,818	52,452	[1]
Stockholders' Equity
Common stock ($2.50 par value; 500,000,000 shares authorized; 273,040,243 shares issued; 270,881,457 and 270,895,902 shares outstanding)	683	683	[1]
Additional paid-in capital	2,221	2,220	[1]
Retained earnings	9,755	9,336	[1]
Accumulated other comprehensive loss	(2,672)	(3,598)	[1]
Treasury stock (2,158,786 and 2,144,341 shares), at cost	(94)	(93)	[1]
Total stockholders’ equity	9,893	8,548	[1]	$ 11,105
Total liabilities and stockholders' equity	$ 64,711	$ 61,000	[1]
Balance Sheet Parenthetical
Common stock, par value (in usd per share)	$ 2.50	$ 2.50
Common stock, shares authorized (in shares	500,000,000	500,000,000
Common stock, shares issued (in shares)	273,040,243	273,040,243
Common stock, shares outstanding (in shares)	270,881,457	270,895,902
Treasury stock, shares (in shares)	2,158,786	2,144,341
Related Party
Assets
Other assets	$ 23	$ 18
Liabilities
Other liabilities	28	26
Parent Company
Assets
Investment in subsidiaries	11,948	10,786
Cash	1	2
Short-term investments	1,009	578
Total assets	12,963	11,370
Liabilities
Short-term debt	550	243
Long-term debt	2,481	2,538
Other liabilities	39	41
Total liabilities	3,070	2,822
Stockholders' Equity
Common stock ($2.50 par value; 500,000,000 shares authorized; 273,040,243 shares issued; 270,881,457 and 270,895,902 shares outstanding)	683	683
Additional paid-in capital	2,221	2,220
Retained earnings	9,755	9,336
Accumulated other comprehensive loss	(2,672)	(3,598)
Treasury stock (2,158,786 and 2,144,341 shares), at cost	(94)	(93)
Total stockholders’ equity	9,893	8,548
Total liabilities and stockholders' equity	12,963	11,370
Parent Company | Related Party
Assets
Other assets	4	4
Parent Company | Nonrelated Party
Assets
Other assets	$ 1	$ 0

[1] As of January 1, 2023, the Company adopted ASU 2018-12, Financial Services-Insurance (Topic 944): Targeted Improvements to the Accounting for Long-Duration Contracts (ASU 2018-12) using the modified retrospective method applied as of the transition date of January 1, 2021. Prior period amounts in the financial statements have been adjusted to reflect application of the new guidance. See Note A to the Consolidated Financial Statements for additional information.