Shareholders' Equity (Details) - USD ($)	3 Months Ended		72 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Feb. 28, 2017	Nov. 30, 2014	Apr. 30, 2012
Common Stock Programs
Shares purchased (in shares)			112,100,000
Total cost of shares purchased	$ 553,000,000	$ 126,000,000	$ 10,100,000,000
Treasury stock acquired, additional transaction costs	$ 2,800,000	$ 600,000
Weighted average shares outstanding
Shares for basic earnings per share (in shares)	248,500,000	264,800,000
Dilutive effect of potentially issuable shares (in shares)	1,700,000	2,200,000
Shares for diluted earnings per share (in shares)	250,200,000	267,000,000
Number of shares excluded from the calculation of diluted earnings per share (in shares)	100,000	0
Share Repurchase Program of 2014
Common Stock Programs
Share repurchase authorization limit (up to)	$ 15,000,000,000.0		15,000,000,000.0	$ 5,000,000,000.0	$ 5,000,000,000.0
Share repurchase, remaining authorization limit (in shares)	$ 4,900,000,000		$ 4,900,000,000
2012 - Share Repurchase Program
Common Stock Programs
Share repurchase authorization limit (up to)						$ 5,000,000,000.0
Shares purchased (in shares)	3,900,000	1,100,000
Average price per share of stock repurchased (in dollars per share)	$ 140.94	$ 114.46
Total cost of shares purchased	$ 550,000,000	$ 125,000,000