Basis of Presentation and Significant Accounting Policies and Practices - Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Basic EPS:
Net income	$ 1,305	$ 1,405	$ 2,522	$ 2,771
Income allocated to RSUs	(9)	(11)	(17)	(23)
Income allocated to common stock for basic EPS	$ 1,296	$ 1,394	$ 2,505	$ 2,748
Weighted average number of shares outstanding, basic (in shares)	937	977	938	980
Basic earnings per common share	$ 1.38	$ 1.43	$ 2.67	$ 2.80
Dilutive effect of stock compensation plans	16	20	16	21
Diluted EPS:
Net income	$ 1,305	$ 1,405	$ 2,522	$ 2,771
Income allocated to RSUs	(8)	(11)	(16)	(22)
Income allocated to common stock for diluted EPS	$ 1,297	$ 1,394	$ 2,506	$ 2,749
Weighted average number of shares outstanding, diluted (in shares)	953	997	954	1,001
Diluted earnings per common share	$ 1.36	$ 1.40	$ 2.63	$ 2.75