Total Equity and Other Comprehensive Income (Rollforward of Total Equity) (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2019		Mar. 31, 2018	Jan. 01, 2019	Dec. 31, 2018	[1]	Jan. 01, 2018	Dec. 31, 2017
Equity [Line Items]
Cumulative effect of new accounting principle in period of adoption							$ (16.0)
Common Stock [Abstract]
Equity, Beginning Balance	$ 47,770.0		$ 47,585.0
Net income	1,271.0		1,239.0
Other comprehensive income (loss), net of tax	720.0		(557.0)
Dividends, Cash [Abstract]
Common	(436.0)		(358.0)
Preferred	(63.0)		(63.0)
Treasury stock activity	(621.0)		(625.0)
Other	(128.0)		(170.0)
Equity, Ending Balance	48,575.0		47,035.0
Preferred stock (less than)	$ 0.5	[1]	$ 0.5		$ 0.5			$ 0.5
Accounting Standards Update 2016-02 [Member]
Equity [Line Items]
Cumulative effect of new accounting principle in period of adoption				$ 62.0
Common Stock [Member]
Common Stock [Abstract]
Beginning Balance (in shares)	457		473
Treasury stock activity, shares	(5)		(3)
Ending Balance, (in shares)	452		470
Equity, Beginning Balance	$ 2,711.0		$ 2,710.0
Dividends, Cash [Abstract]
Equity, Ending Balance	2,711.0		2,710.0
Capital Surplus - Preferred Stock [Member]
Common Stock [Abstract]
Equity, Beginning Balance	3,986.0		3,985.0
Dividends, Cash [Abstract]
Preferred stock discount accretion	1.0		1.0
Other	3.0
Equity, Ending Balance	3,990.0		3,986.0
Capital Surplus - Common Stock and Other [Member]
Common Stock [Abstract]
Equity, Beginning Balance	12,291.0		12,389.0
Dividends, Cash [Abstract]
Treasury stock activity	10.0		6.0
Other	(118.0)		(154.0)
Equity, Ending Balance	12,183.0		12,241.0
Retained Earnings [Member]
Equity [Line Items]
Cumulative effect of new accounting principle in period of adoption							(22.0)
Common Stock [Abstract]
Equity, Beginning Balance	38,919.0		35,481.0
Net income	1,261.0		1,229.0
Dividends, Cash [Abstract]
Common	(436.0)		(358.0)
Preferred	(63.0)		(63.0)
Preferred stock discount accretion	(1.0)		(1.0)
Equity, Ending Balance	39,742.0		36,266.0
Retained Earnings [Member] | Accounting Standards Update 2016-02 [Member]
Equity [Line Items]
Cumulative effect of new accounting principle in period of adoption				$ 62.0
Accumulated Other Comprehensive Income (Loss) [Member]
Equity [Line Items]
Cumulative effect of new accounting principle in period of adoption							$ 6.0
Common Stock [Abstract]
Equity, Beginning Balance	(725.0)		(148.0)
Other comprehensive income (loss), net of tax	720.0		(557.0)
Dividends, Cash [Abstract]
Equity, Ending Balance	(5.0)		(699.0)
Treasury Stock [Member]
Common Stock [Abstract]
Equity, Beginning Balance	(9,454.0)		(6,904.0)
Dividends, Cash [Abstract]
Treasury stock activity	(631.0)		(631.0)
Equity, Ending Balance	(10,085.0)		(7,535.0)
Noncontrolling Interest [Member]
Common Stock [Abstract]
Equity, Beginning Balance	42.0		72.0
Net income	10.0		10.0
Dividends, Cash [Abstract]
Other	(13.0)		(16.0)
Equity, Ending Balance	$ 39.0		$ 66.0

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