Stockholders' Equity - Changes in Stockholders' Equity (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
	Mar. 02, 2015	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Stock Repurchase Program, Number of Shares Authorized to be Repurchased	20,000,000
Changes in Stockholders' Equity
Beginning Balance				$ 20,926	$ 19,764
Net income after dividends on preferred and preference stock		$ 959	$ 718	2,096	1,680
Other comprehensive income (loss)				(7)	6
Treasury stock re-issued					225
Stock issued				136	332
Stock-based compensation				78
Stock repurchased, at cost, Shares	(2,600,000)
Stock repurchased, at cost				(115)	(5)
Cash dividends on common stock				(1,465)	(1,390)
Preference stock redemption				(150)
Contributions from noncontrolling interest				429
Distributions to noncontrolling interest				(13)
Net income attributable to noncontrolling interest				13
Other				(5)	1
Ending Balance		$ 21,923	$ 20,613	$ 21,923	$ 20,613
Number of Common shares Issued [Member]
Changes in Stockholders' Equity
Beginning Balance, Shares				908,502,000	892,733,000
Stock issued, Shares				3,769,000	7,781,000
Ending Balance, Shares		912,271,000	900,514,000	912,271,000	900,514,000
Number of Common shares Treasury [Member]
Changes in Stockholders' Equity
Beginning Balance, Shares				725,000	5,647,000
Treasury stock re-issued, Shares					4,996,000
Stock repurchased, at cost, Shares				(2,599,000)
Other, Shares				(8,000)	(51,000)
Ending Balance, Shares		3,332,000	702,000	3,332,000	702,000
Common Stockholders' Equity [Member]
Changes in Stockholders' Equity
Beginning Balance				$ 19,949	$ 19,008
Net income after dividends on preferred and preference stock				2,096	1,680
Other comprehensive income (loss)				(7)	6
Treasury stock re-issued					225
Stock issued				136	332
Stock-based compensation				78
Stock repurchased, at cost				(115)	(5)
Cash dividends on common stock				(1,465)	(1,390)
Other				(8)	1
Ending Balance		$ 20,664	$ 19,857	20,664	19,857
Preferred And Preference Stock [Member]
Changes in Stockholders' Equity
Beginning Balance				756	756
Stock issued					0
Preference stock redemption				(150)
Other				3
Ending Balance		609	$ 756	609	$ 756
Noncontrolling Interest [Member]
Changes in Stockholders' Equity
Beginning Balance				221
Contributions from noncontrolling interest				429
Distributions to noncontrolling interest				(13)
Net income attributable to noncontrolling interest				13
Ending Balance		$ 650		$ 650