Earnings Per Share of Common Stock - Computation (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Number of shares on which basic earnings per share is calculated:
Weighted-average shares outstanding during period (in shares)	889,581,542	920,680,222
Add - Incremental shares under stock-based compensation plans (in shares)	3,372,460	3,553,104
Add - Incremental shares associated with contingently issuable shares (in shares)	956,524	1,176,108
Number of shares on which diluted earnings per share is calculated (in shares)	893,910,526	925,409,434
Net income on which basic earnings per share is calculated
Income from continuing operations	$ 1,593	$ 1,675
Income/(loss) from discontinued operations, net of tax	(2)	4
Net income on which basic earnings per share is calculated	1,591	1,679
Net income on which diluted earnings per share is calculated
Income from continuing operations	1,593	1,675
Income from continuing operations on which diluted earnings per share is calculated	1,593	1,675
Income/(loss) from discontinued operations, net of tax, on which basic and diluted earnings per share is calculated	(2)	4
Net income on which diluted earnings per share is calculated	$ 1,591	$ 1,679
Assuming dilution
Continuing operations (in dollars per share)	$ 1.78	$ 1.81
Discontinued operations (in dollars per share)	0.00	0.00
Total (in dollars per share)	1.78	1.81
Basic
Continuing operations (in dollars per share)	1.79	1.82
Discontinued operations (in dollars per share)	0.00	0.00
Total (in dollars per share)	$ 1.79	$ 1.82