Total Equity and Other Comprehensive Income (Rollforward of Total Equity) (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2019		Sep. 30, 2018	Sep. 30, 2019		Sep. 30, 2018	Dec. 31, 2018		Mar. 31, 2018	Dec. 31, 2017
Common Stock [Abstract]
Equity, Beginning Balance	$ 49,381.0		$ 46,975.0	$ 47,770.0		$ 47,585.0
Cumulative effect of new accounting principle in period of adoption										$ (16.0)
Adjusted opening balance							$ 47,832.0			47,569.0
Net income	1,392.0		1,400.0	4,037.0		3,995.0
Other comprehensive income (loss), net of tax	206.0		(320.0)	1,562.0		(1,118.0)
Dividends, Cash [Abstract]
Common	(518.0)		(446.0)	(1,386.0)		(1,159.0)
Preferred	(63.0)		(63.0)	(181.0)		(181.0)
Common stock activity			1.0	10.0		10.0
Treasury stock activity	(977.0)		(459.0)	(2,380.0)		(1,898.0)
Other	34.0		14.0	(39.0)		(116.0)
Equity, Ending Balance	49,455.0		47,102.0	49,455.0		47,102.0
Preferred stock (less than)	$ 0.5	[1]	$ 0.5	$ 0.5	[1]	$ 0.5	0.5	[1]	$ 0.5
Accounting Standards Update 2016-02 [Member]
Common Stock [Abstract]
Cumulative effect of new accounting principle in period of adoption							62.0
Common Stock, par value $5.00
Common Stock [Abstract]
Beginning Balance (in shares)	447		465	457		473
Treasury stock activity, shares	(8)		(3)	(18)		(11)
Ending Balance, (in shares)	439		462	439		462
Equity, Beginning Balance	$ 2,711.0		$ 2,710.0	$ 2,711.0		$ 2,710.0
Adjusted opening balance							2,711.0			2,710.0
Dividends, Cash [Abstract]
Equity, Ending Balance	2,711.0		2,710.0	2,711.0		2,710.0
Capital Surplus - Preferred Stock [Member]
Common Stock [Abstract]
Equity, Beginning Balance	3,991.0		3,987.0	3,986.0		3,985.0
Adjusted opening balance							3,986.0			3,985.0
Dividends, Cash [Abstract]
Preferred stock discount accretion	1.0		1.0	3.0		3.0
Other			(6.0)	3.0		(6.0)
Equity, Ending Balance	3,992.0		3,982.0	3,992.0		3,982.0
Capital Surplus - Common Stock and Other [Member]
Common Stock [Abstract]
Equity, Beginning Balance	12,257.0		12,263.0	12,291.0		12,389.0
Adjusted opening balance							12,291.0			12,389.0
Dividends, Cash [Abstract]
Common stock activity			1.0	10.0		10.0
Treasury stock activity	(5.0)		(5.0)	4.0		(31.0)
Other	53.0		58.0			(51.0)
Equity, Ending Balance	12,305.0		12,317.0	12,305.0		12,317.0
Retained Earnings [Member]
Common Stock [Abstract]
Equity, Beginning Balance	40,616.0		37,201.0	38,919.0		35,481.0
Cumulative effect of new accounting principle in period of adoption										(22.0)
Adjusted opening balance							38,981.0			35,459.0
Net income	1,379.0		1,389.0	4,002.0		3,964.0
Dividends, Cash [Abstract]
Common	(518.0)		(446.0)	(1,386.0)		(1,159.0)
Preferred	(63.0)		(63.0)	(181.0)		(181.0)
Preferred stock discount accretion	(1.0)		(1.0)	(3.0)		(3.0)
Equity, Ending Balance	41,413.0		38,080.0	41,413.0		38,080.0
Retained Earnings [Member] | Accounting Standards Update 2016-02 [Member]
Common Stock [Abstract]
Cumulative effect of new accounting principle in period of adoption							62.0
Accumulated Other Comprehensive Income (Loss) [Member]
Common Stock [Abstract]
Equity, Beginning Balance	631.0		(940.0)	(725.0)		(148.0)
Cumulative effect of new accounting principle in period of adoption										6.0
Adjusted opening balance							(725.0)			(142.0)
Other comprehensive income (loss), net of tax	206.0		(320.0)	1,562.0		(1,118.0)
Dividends, Cash [Abstract]
Equity, Ending Balance	837.0		(1,260.0)	837.0		(1,260.0)
Treasury Stock [Member]
Common Stock [Abstract]
Equity, Beginning Balance	(10,866.0)		(8,317.0)	(9,454.0)		(6,904.0)
Adjusted opening balance							(9,454.0)			(6,904.0)
Dividends, Cash [Abstract]
Treasury stock activity	(972.0)		(454.0)	(2,384.0)		(1,867.0)
Equity, Ending Balance	(11,838.0)		(8,771.0)	(11,838.0)		(8,771.0)
Noncontrolling Interest [Member]
Common Stock [Abstract]
Equity, Beginning Balance	41.0		71.0	42.0		72.0
Adjusted opening balance							$ 42.0			$ 72.0
Net income	13.0		11.0	35.0		31.0
Dividends, Cash [Abstract]
Other	(19.0)		(38.0)	(42.0)		(59.0)
Equity, Ending Balance	$ 35.0		$ 44.0	$ 35.0		$ 44.0

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