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, 2018		Mar. 31, 2017	Dec. 31, 2017
Cumulative effect of ASU adoptions				$ (16)
Common Stock [Abstract]
Common Stock, Beginning Balance	$ 2,710
Retained Earnings, Beginning Balance	35,481
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance	(148)		$ (265)
Treasury Stock, Beginning Balance	6,904
Noncontrolling interests, Beginning Balance	72
Total Equity, Beginning Balance, Adjusted				47,569
Total Equity, Beginning Balance	47,585		46,854
Net income	1,239		1,074
Other comprehensive income (loss), net of tax	(557)		(14)
Dividends, Cash [Abstract]
Common	(358)		(271)
Preferred	(63)		(63)
Redemptions of noncontrolling interests			(1,000)
Treasury stock activity	(625)		(473)
Other	(170)		(204)
Common Stock, Ending Balance	2,710
Retained Earnings, Ending Balance	36,266
Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance	(699)		(279)
Treasury Stock, Ending Balance	7,535
Noncontrolling interests, Ending Balance	66
Total Equity, Ending Balance	$ 47,035		$ 45,903
Cash dividends declared, Common, per share (in dollars per share)	$ 0.75		$ 0.55
Par value less than $.5 million at each date		[1]			[1]
Common Stock [Member]
Common Stock [Abstract]
Beginning Balance (in shares)	473.0		485.0
Treasury stock activity, shares	(3.0)
Ending Balance, (in shares)	470.0		485.0
Common Stock, Beginning Balance	$ 2,710		$ 2,709
Dividends, Cash [Abstract]
Treasury stock activity, less than .5 million shares
Common Stock, Ending Balance	$ 2,710		$ 2,709
Common stock activity (less than .5 million shares)	0.5
Preferred Stock Including Additional Paid in Capital [Member]
Common Stock [Abstract]
Capital surplus - Preferred Stock, Beginning Balance	$ 3,985		3,977
Dividends, Cash [Abstract]
Preferred stock discount accretion	1		2
Capital surplus - Preferred Stock, Ending Balance	3,986		3,979
Common Stock Including Additional Paid in Capital [Member]
Common Stock [Abstract]
Capital surplus - Common Stock, Beginning Balance	12,389		12,674
Dividends, Cash [Abstract]
Treasury stock activity	6		(216)
Other	(154)		(162)
Capital surplus - Common Stock, Ending Balance	12,241		12,296
Retained Earnings [Member]
Cumulative effect of ASU adoptions				(22)
Common Stock [Abstract]
Retained Earnings, Beginning Balance	35,459		31,670
Net income	1,229		1,057
Dividends, Cash [Abstract]
Common	(358)		(271)
Preferred	(63)		(63)
Preferred stock discount accretion	(1)		(2)
Redemptions of noncontrolling interests			(19)
Retained Earnings, Ending Balance	36,266		32,372
Accumulated Other Comprehensive Income (Loss) [Member]
Cumulative effect of ASU adoptions				$ 6
Common Stock [Abstract]
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance	(142)		(265)
Other comprehensive income (loss), net of tax	(557)		(14)
Dividends, Cash [Abstract]
Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance	(699)		(279)
Treasury Stock [Member]
Common Stock [Abstract]
Treasury Stock, Beginning Balance	(6,904)		(5,066)
Dividends, Cash [Abstract]
Treasury stock activity	(631)		(257)
Treasury Stock, Ending Balance	(7,535)		(5,323)
Noncontrolling Interest [Member]
Common Stock [Abstract]
Noncontrolling interests, Beginning Balance	72		1,155
Net income	10		17
Dividends, Cash [Abstract]
Redemptions of noncontrolling interests			(981)
Other	(16)		(42)
Noncontrolling interests, Ending Balance	$ 66		$ 149
As Previously Reported [Member] | Common Stock [Member]
Common Stock [Abstract]
Beginning Balance (in shares)	473.0
Common Stock, Beginning Balance	$ 2,710
As Previously Reported [Member] | Preferred Stock Including Additional Paid in Capital [Member]
Common Stock [Abstract]
Capital surplus - Preferred Stock, Beginning Balance	3,985
As Previously Reported [Member] | Common Stock Including Additional Paid in Capital [Member]
Common Stock [Abstract]
Capital surplus - Common Stock, Beginning Balance	12,389
As Previously Reported [Member] | Retained Earnings [Member]
Common Stock [Abstract]
Retained Earnings, Beginning Balance	35,481
As Previously Reported [Member] | Accumulated Other Comprehensive Income (Loss) [Member]
Common Stock [Abstract]
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance	(148)
As Previously Reported [Member] | Treasury Stock [Member]
Common Stock [Abstract]
Treasury Stock, Beginning Balance	(6,904)
As Previously Reported [Member] | Noncontrolling Interest [Member]
Common Stock [Abstract]
Noncontrolling interests, Beginning Balance	$ 72

[1] Par value less than $.5 million at each date.