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Equity impact of the value of stock that has been repurchased during the period and has not been retired and is not held in treasury. Some state laws may mandate the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity.

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Total Equity and Other Comprehensive Income (Rollforward of Total Equity) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 01, 2020	Jan. 01, 2020	Dec. 31, 2019	Jun. 30, 2019	Jan. 01, 2019
Common Stock [Abstract]
Equity, Beginning Balance	$ 52,948.0		$ 49,343.0	$ 47,770.0
Adjusted opening balance						$ 48,672.0		$ 49,381.0	$ 47,832.0
Net income	1,532.0	$ 1,392.0	6,102.0	4,037.0
Other comprehensive income (loss), net of tax	(72.0)	206.0	2,198.0	1,562.0
Dividends, Cash [Abstract]
Common	(494.0)	(518.0)	(1,488.0)	(1,386.0)
Preferred	(63.0)	(63.0)	(181.0)	(181.0)
Common stock activity			11.0	10.0
Treasury stock activity	(87.0)	(977.0)	(1,383.0)	(2,380.0)
Preferred stock redemption - Series Q	(480.0)		(480.0)
Other	26.0	34.0	(141.0)	(39.0)
Equity, Ending Balance	53,310.0	49,455.0	53,310.0	49,455.0
Preferred stock (less than)	$ 0.5	$ 0.5	$ 0.5	$ 0.5			$ 0.5
Common stock held in treasury at cost (shares)	118,000,000		118,000,000				109,000,000
Series Q Preferred Stock [Member]
Dividends, Cash [Abstract]
Treasury Stock, Preferred, Shares					4,800
Depositary Shares [Member]
Dividends, Cash [Abstract]
Common stock held in treasury at cost (shares)					19,200,000
Accounting Standards Update 2016-02
Common Stock [Abstract]
Cumulative effect of new accounting principle in period of adoption									62.0
Accounting Standards Update 2016-13
Common Stock [Abstract]
Cumulative effect of new accounting principle in period of adoption						(671.0)
Common Stock, par value $5.00
Common Stock [Abstract]
Beginning Balance (in shares)	425,000,000	447,000,000	433,000,000	457,000,000
Treasury stock activity, shares	(1,000,000)	(8,000,000)	(9,000,000)	(18,000,000)
Ending Balance, (in shares)	424,000,000	439,000,000	424,000,000	439,000,000
Equity, Beginning Balance	$ 2,712.0		$ 2,712.0	$ 2,711.0
Adjusted opening balance						2,712.0		2,711.0	2,711.0
Dividends, Cash [Abstract]
Equity, Ending Balance	2,712.0	$ 2,711.0	2,712.0	2,711.0
Capital Surplus - Preferred Stock [Member]
Common Stock [Abstract]
Equity, Beginning Balance	3,995.0		3,993.0	3,986.0
Adjusted opening balance						3,993.0		3,991.0	3,986.0
Dividends, Cash [Abstract]
Preferred stock discount accretion	1.0	1.0	3.0	3.0
Preferred stock redemption - Series Q	(480.0)		(480.0)
Other				3.0
Equity, Ending Balance	3,516.0	3,992.0	3,516.0	3,992.0
Capital Surplus - Common Stock and Other [Member]
Common Stock [Abstract]
Equity, Beginning Balance	12,289.0		12,376.0	12,291.0
Adjusted opening balance						12,376.0		12,257.0	12,291.0
Dividends, Cash [Abstract]
Common stock activity			11.0	10.0
Treasury stock activity	1.0	(5.0)	52.0	4.0
Other	30.0	53.0	(119.0)
Equity, Ending Balance	12,320.0	12,305.0	12,320.0	12,305.0
Retained Earnings [Member]
Common Stock [Abstract]
Equity, Beginning Balance	44,986.0		42,215.0	38,919.0
Adjusted opening balance						41,544.0		40,616.0	38,981.0
Net income	1,519.0	1,379.0	6,075.0	4,002.0
Dividends, Cash [Abstract]
Common	(494.0)	(518.0)	(1,488.0)	(1,386.0)
Preferred	(63.0)	(63.0)	(181.0)	(181.0)
Preferred stock discount accretion	(1.0)	(1.0)	(3.0)	(3.0)
Equity, Ending Balance	45,947.0	41,413.0	45,947.0	41,413.0
Retained Earnings [Member] \| Accounting Standards Update 2016-02
Common Stock [Abstract]
Cumulative effect of new accounting principle in period of adoption									62.0
Retained Earnings [Member] \| Accounting Standards Update 2016-13
Common Stock [Abstract]
Cumulative effect of new accounting principle in period of adoption						(671.0)
Accumulated Other Comprehensive Income (Loss) [Member]
Common Stock [Abstract]
Equity, Beginning Balance	3,069.0	631.0	799.0	(725.0)
Adjusted opening balance						799.0		631.0	(725.0)
Other comprehensive income (loss), net of tax	(72.0)	206.0	2,198.0	1,562.0
Dividends, Cash [Abstract]
Equity, Ending Balance	2,997.0	837.0	2,997.0	837.0
Treasury Stock [Member]
Common Stock [Abstract]
Equity, Beginning Balance	(14,128.0)		(12,781.0)	(9,454.0)
Adjusted opening balance						(12,781.0)		(10,866.0)	(9,454.0)
Dividends, Cash [Abstract]
Treasury stock activity	(88.0)	(972.0)	(1,435.0)	(2,384.0)
Equity, Ending Balance	(14,216.0)	(11,838.0)	(14,216.0)	(11,838.0)
Noncontrolling Interest [Member]
Common Stock [Abstract]
Equity, Beginning Balance	25.0		29.0	42.0
Adjusted opening balance						$ 29.0		$ 41.0	$ 42.0
Net income	13.0	13.0	27.0	35.0
Dividends, Cash [Abstract]
Other	(4.0)	(19.0)	(22.0)	(42.0)
Equity, Ending Balance	$ 34.0	$ 35.0	$ 34.0	$ 35.0