Earnings Per Share of Common Stock - Computation (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Number of shares on which basic earnings per share is calculated:
Weighted-average shares outstanding during period (in shares)	886,273,682	915,064,434	887,927,612	917,872,328
Add - Incremental shares under stock-based compensation plans (in shares)	3,281,570	2,882,043	3,327,015	3,217,574
Add - Incremental shares associated with contingently issuable shares (in shares)	1,276,549	1,452,129	1,116,537	1,314,118
Number of shares on which diluted earnings per share is calculated (in shares)	890,831,801	919,398,606	892,371,164	922,404,020
Net income on which basic earnings per share is calculated
Income from continuing operations	$ 2,499	$ 2,402	$ 4,093	$ 4,078
Income/(loss) from discontinued operations, net of tax	(1)	1	(4)	5
Net income on which basic earnings per share is calculated	2,498	2,404	4,089	4,083
Net income on which diluted earnings per share is calculated
Income from continuing operations	2,499	2,402	4,093	4,078
Net income applicable to contingently issuable shares	0	(1)	0	(1)
Income from continuing operations on which diluted earnings per share is calculated	2,500	2,401	4,093	4,077
Income/(loss) from discontinued operations, net of tax, on which basic and diluted earnings per share is calculated	(1)	1	(4)	5
Net income on which diluted earnings per share is calculated	$ 2,499	$ 2,403	$ 4,090	$ 4,082
Assuming dilution
Continuing operations (in dollars per share)	$ 2.81	$ 2.61	$ 4.58	$ 4.42
Discontinued operations (in dollars per share)	0.00	0.00	0.00	0.01
Total (in dollars per share)	2.81	2.61	4.58	4.43
Basic
Continuing operations (in dollars per share)	2.82	2.63	4.61	4.44
Discontinued operations (in dollars per share)	0.00	0.00	0.00	0.01
Total (in dollars per share)	$ 2.82	$ 2.63	$ 4.61	$ 4.45