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, 2021	Dec. 31, 2020	Dec. 31, 2019
Assets
Cash	$ 536	$ 419
Other assets	2,261	1,628
Total assets	66,639	64,026
Liabilities
Long term debt	2,779	2,776
Other liabilities	3,377	3,377
Total liabilities	53,830	51,319
Stockholders' Equity
Common stock ($2.50 par value; 500,000,000 shares authorized; 273,040,243 shares issued; 271,363,999 and 271,391,603 shares outstanding)	683	683
Additional paid-in capital	2,215	2,211
Retained earnings	9,663	9,081
Accumulated other comprehensive income	320	803
Treasury stock (1,676,244 and 1,648,640 shares), at cost	(72)	(71)
Total stockholders’ equity	12,809	12,707	$ 12,215
Total liabilities and stockholders' equity	$ 66,639	$ 64,026
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)	271,363,999	271,391,603
Treasury stock, shares (in shares)	1,676,244	1,648,640
Parent Company
Assets
Investment in subsidiaries	$ 14,937	$ 14,996
Cash	1	0
Short term investments	685	522
Amounts due from affiliates	3	4
Other assets	0	1
Total assets	15,626	15,523
Liabilities
Long term debt	2,779	2,776
Other liabilities	38	40
Total liabilities	2,817	2,816
Stockholders' Equity
Common stock ($2.50 par value; 500,000,000 shares authorized; 273,040,243 shares issued; 271,363,999 and 271,391,603 shares outstanding)	683	683
Additional paid-in capital	2,215	2,211
Retained earnings	9,663	9,081
Accumulated other comprehensive income	320	803
Treasury stock (1,676,244 and 1,648,640 shares), at cost	(72)	(71)
Total stockholders’ equity	12,809	12,707
Total liabilities and stockholders' equity	$ 15,626	$ 15,523