Total Equity and Other Comprehensive Income (Rollforward of Total Equity) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Common Stock [Abstract]
Common Stock, Beginning Balance	$ 2,708
Capital surplus - Preferred Stock, Beginning Balance	3,452
Capital surplus - Common Stock, Beginning Balance	12,745
Retained Earnings, Beginning Balance	29,043
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance	130	$ 503
Treasury Stock, Beginning Balance	3,368
Noncontrolling interests, Beginning Balance	1,270
Total Equity, Beginning Balance	45,980	46,074
Net income	943	1,004
Other comprehensive income (loss), net of tax	402	200
Cash dividends declared [Abstract]
Common	(260)	(251)
Preferred	(64)	(68)
Common stock activity	2	9
Treasury stock activity	(434)	(363)
Other	(241)	(167)
Common Stock, Ending Balance	2,708
Capital surplus - Preferred Stock, Ending Balance	3,453
Capital surplus - Common Stock, Ending Balance	12,586
Retained Earnings, Ending Balance	29,642
Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance	532	703
Treasury Stock, Ending Balance	3,791
Noncontrolling interests, Ending Balance	1,198
Total Equity, Ending Balance	$ 46,328	$ 46,438
Common Stock [Member]
Common Stock [Abstract]
Beginning Balance (in shares)	504	523
Treasury stock activity, shares	(5)	(3)
Ending Balance, (in shares)	499	520
Common Stock, Beginning Balance	$ 2,708	$ 2,705
Cash dividends declared [Abstract]
Common stock activity		1
Common Stock, Ending Balance	$ 2,708	$ 2,706
Common Stock Per Share Dividends Declared	$ 0.51	$ 0.48
Preferred Stock Including Additional Paid in Capital [Member]
Common Stock [Abstract]
Capital surplus - Preferred Stock, Beginning Balance	$ 3,452	$ 3,946
Cash dividends declared [Abstract]
Preferred stock discount accretion	1	2
Capital surplus - Preferred Stock, Ending Balance	3,453	3,948
Common Stock Including Additional Paid in Capital [Member]
Common Stock [Abstract]
Capital surplus - Common Stock, Beginning Balance	12,745	12,627
Cash dividends declared [Abstract]
Common stock activity	2	8
Treasury stock activity	(11)	(18)
Other	(150)	(56)
Capital surplus - Common Stock, Ending Balance	12,586	12,561
Retained Earnings [Member]
Common Stock [Abstract]
Retained Earnings, Beginning Balance	29,043	26,200
Net income	924	1,003
Cash dividends declared [Abstract]
Common	(260)	(251)
Preferred	(64)	(68)
Preferred stock discount accretion	(1)	(2)
Retained Earnings, Ending Balance	29,642	26,882
Accumulated Other Comprehensive Income (Loss) [Member]
Common Stock [Abstract]
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance	130	503
Other comprehensive income (loss), net of tax	402	200
Cash dividends declared [Abstract]
Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance	532	703
Treasury Stock [Member]
Common Stock [Abstract]
Treasury Stock, Beginning Balance	(3,368)	(1,430)
Cash dividends declared [Abstract]
Treasury stock activity	(423)	(345)
Treasury Stock, Ending Balance	(3,791)	(1,775)
Noncontrolling Interest [Member]
Common Stock [Abstract]
Noncontrolling interests, Beginning Balance	1,270	1,523
Net income	19	1
Cash dividends declared [Abstract]
Other	(91)	(111)
Noncontrolling interests, Ending Balance	$ 1,198	$ 1,413