Common and Preferred Shares (Details) - shares shares in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Equity [Abstract]
Common shares, authorized (in shares)	3,600	3,600	3,600
Schedule Of Stock By Class [Roll Forward]
Shares issued and outstanding at beginning of year (in shares)	761	805	810
Repurchases of common shares (in shares)	(20)	(46)	(7)
Other, primarily stock option exercises and restricted stock awards granted (in shares)	2	2	2
Shares issued and outstanding as of December 31 (in shares)	743	761	805
Shares reserved for issuance under employee stock and employee benefit plans (in shares)	18