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, 2025	Dec. 31, 2024	Dec. 31, 2023
Assets
Cash	$ 425	$ 472
Other assets	2,760	2,591
Total assets	69,443	66,492
Liabilities
Long-term debt	2,971	2,973
Other liabilities	3,031	2,996
Total liabilities	57,822	55,979
Stockholders' Equity
Common stock ($2.50 par value; 500,000,000 shares authorized; 273,040,243 shares issued; 270,671,747 and 270,844,681 shares outstanding)	683	683
Additional paid-in capital	2,229	2,229
Retained earnings	9,915	9,686
Accumulated other comprehensive loss	(1,098)	(1,991)
Treasury stock (2,368,496 and 2,195,562 shares), at cost	(108)	(94)
Total stockholders’ equity	11,621	10,513	$ 9,893
Total liabilities and stockholders' equity	$ 69,443	$ 66,492
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)	270,671,747	270,844,681
Treasury stock, shares (in shares)	2,368,496	2,195,562
Related Party
Assets
Other assets		$ 17
Liabilities
Other liabilities	$ 54	47
Parent Company
Assets
Investment in subsidiaries	13,845	12,684
Cash	1	1
Short-term investments	796	846
Total assets	14,646	13,536
Liabilities
Long-term debt	2,971	2,973
Other liabilities	54	50
Total liabilities	3,025	3,023
Stockholders' Equity
Common stock ($2.50 par value; 500,000,000 shares authorized; 273,040,243 shares issued; 270,671,747 and 270,844,681 shares outstanding)	683	683
Additional paid-in capital	2,229	2,229
Retained earnings	9,915	9,686
Accumulated other comprehensive loss	(1,098)	(1,991)
Treasury stock (2,368,496 and 2,195,562 shares), at cost	(108)	(94)
Total stockholders’ equity	11,621	10,513
Total liabilities and stockholders' equity	14,646	13,536
Parent Company | Related Party
Assets
Other assets	3	4
Parent Company | Nonrelated Party
Assets
Other assets	$ 1	$ 1