Earnings Per Share of Common Stock - Computation (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Weighted-average number of shares on which earnings per share calculations are based
Weighted-average shares outstanding during period (in shares)	893,630,916	887,969,345
Add - Incremental shares under stock-based compensation plans (in shares)	6,622,441	5,740,415
Add - Incremental shares associated with contingently issuable shares (in shares)	1,492,709	1,329,477
Assuming dilution (in shares)	901,746,065	895,039,238
Net income on which basic earnings per share is calculated
Income from continuing operations	$ 956	$ 1,176
Income/(loss) from discontinued operations, net of tax	(1)	(1)
Net income on which basic earnings per share is calculated	955	1,175
Net income on which diluted earnings per share is calculated
Income from continuing operations	956	1,176
Net income applicable to contingently issuable shares		(2)
Income from continuing operations on which diluted earnings per share is calculated	956	1,174
Income/(loss) from discontinued operations, net of tax, on which basic and diluted earnings per share is calculated	(1)	(1)
Net income on which diluted earnings per share is calculated	$ 955	$ 1,173
Assuming dilution
Continuing operations (in dollars per share)	$ 1.06	$ 1.31
Discontinued operations (in dollars per share)	0.00	0.00
Total (in dollars per share)	1.06	1.31
Basic
Continuing operations (in dollars per share)	1.07	1.32
Discontinued operations (in dollars per share)	0.00	0.00
Total (in dollars per share)	$ 1.07	$ 1.32