Total Equity and Other Comprehensive Income (Rollforward of Total Equity) (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2020		Mar. 31, 2019	Jan. 01, 2020	Dec. 31, 2019	[1]	Jan. 01, 2019
Common Stock [Abstract]
Equity, Beginning Balance	$ 49,343.0		$ 47,770.0
Cumulative effect of new accounting principle in period of adoption				$ (671.0)			$ 62.0
Adjusted opening balance				48,672.0			47,832.0
Net income	915.0		1,271.0
Other comprehensive income (loss), net of tax	1,719.0		720.0
Dividends, Cash [Abstract]
Common	(503.0)		(436.0)
Preferred	(63.0)		(63.0)
Common stock activity
Treasury stock activity	(1,310.0)		(621.0)
Other	(140.0)		(128.0)
Equity, Ending Balance	49,290.0		48,575.0
Preferred stock (less than)	$ 0.5	[1]	$ 0.5		$ 0.5
Common Stock, par value $5.00
Common Stock [Abstract]
Beginning Balance (in shares)	433		457
Treasury stock activity, shares	(9)		(5)
Ending Balance, (in shares)	424		452
Equity, Beginning Balance	$ 2,712.0		$ 2,711.0
Adjusted opening balance				2,712.0			2,711.0
Dividends, Cash [Abstract]
Equity, Ending Balance	2,712.0		2,711.0
Capital Surplus - Preferred Stock [Member]
Common Stock [Abstract]
Equity, Beginning Balance	3,993.0		3,986.0
Adjusted opening balance				3,993.0			3,986.0
Dividends, Cash [Abstract]
Preferred stock discount accretion	1.0		1.0
Other			3.0
Equity, Ending Balance	3,994.0		3,990.0
Capital Surplus - Common Stock and Other [Member]
Common Stock [Abstract]
Equity, Beginning Balance	12,376.0		12,291.0
Adjusted opening balance				12,376.0			12,291.0
Dividends, Cash [Abstract]
Common stock activity
Treasury stock activity	49.0		10.0
Other	(131.0)		(118.0)
Equity, Ending Balance	12,294.0		12,183.0
Retained Earnings [Member]
Common Stock [Abstract]
Equity, Beginning Balance	42,215.0		38,919.0
Cumulative effect of new accounting principle in period of adoption				(671.0)			62.0
Adjusted opening balance				41,544.0			38,981.0
Net income	908.0		1,261.0
Dividends, Cash [Abstract]
Common	(503.0)		(436.0)
Preferred	(63.0)		(63.0)
Preferred stock discount accretion	(1.0)		(1.0)
Equity, Ending Balance	41,885.0		39,742.0
Accumulated Other Comprehensive Income (Loss) [Member]
Common Stock [Abstract]
Equity, Beginning Balance	799.0		(725.0)
Cumulative effect of new accounting principle in period of adoption				0.0
Adjusted opening balance				799.0			(725.0)
Other comprehensive income (loss), net of tax	1,719.0		720.0
Dividends, Cash [Abstract]
Equity, Ending Balance	2,518.0		(5.0)
Treasury Stock [Member]
Common Stock [Abstract]
Equity, Beginning Balance	(12,781.0)		(9,454.0)
Adjusted opening balance				(12,781.0)			(9,454.0)
Dividends, Cash [Abstract]
Treasury stock activity	(1,359.0)		(631.0)
Equity, Ending Balance	(14,140.0)		(10,085.0)
Noncontrolling Interest [Member]
Common Stock [Abstract]
Equity, Beginning Balance	29.0		42.0
Adjusted opening balance				$ 29.0			$ 42.0
Net income	7.0		10.0
Dividends, Cash [Abstract]
Other	(9.0)		(13.0)
Equity, Ending Balance	$ 27.0		$ 39.0

[1] Amounts include our equity investment in BlackRock.