Total Equity and Other Comprehensive Income (Rollforward of Total Equity) (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021	Dec. 31, 2020
Common Stock [Abstract]
Equity, Beginning Balance	$ 55,726.0	$ 54,041.0
Net income	1,429.0	1,826.0
Other comprehensive income (loss), net of tax	(6,140.0)	(1,480.0)
Dividends, Cash [Abstract]
Common	(531.0)	(493.0)
Preferred	(45.0)	(57.0)
Preferred stock discount accretion
Treasury stock activity	(1,189.0)	128.0
Other	(34.0)	(86.0)
Equity, Ending Balance	49,216.0	$ 53,879.0
Par value less than $.5 million at each date	$ 0.5		$ 0.5	$ 0.5
Common Stock
Common Stock [Abstract]
Beginning Balance (in shares)	420	424
Treasury stock activity, shares	(5)	1
Ending Balance, (in shares)	415	425
Equity, Beginning Balance	$ 2,713.0	$ 2,713.0
Dividends, Cash [Abstract]
Equity, Ending Balance	2,713.0	2,713.0
Capital Surplus - Preferred Stock
Common Stock [Abstract]
Equity, Beginning Balance	5,009.0	3,517.0
Dividends, Cash [Abstract]
Preferred stock discount accretion	2.0	1.0
Equity, Ending Balance	5,011.0	3,518.0
Capital Surplus - Common Stock and Other
Common Stock [Abstract]
Equity, Beginning Balance	12,448.0	12,367.0
Dividends, Cash [Abstract]
Treasury stock activity	45.0	69.0
Other	(17.0)	(75.0)
Equity, Ending Balance	12,476.0	12,361.0
Retained Earnings
Common Stock [Abstract]
Equity, Beginning Balance	50,228.0	46,848.0
Net income	1,408.0	1,816.0
Dividends, Cash [Abstract]
Common	(531.0)	(493.0)
Preferred	(45.0)	(57.0)
Preferred stock discount accretion	(2.0)	(1.0)
Equity, Ending Balance	51,058.0	48,113.0
Accumulated Other Comprehensive Income (Loss)
Common Stock [Abstract]
Equity, Beginning Balance	409.0	2,770.0
Other comprehensive income (loss), net of tax	(6,140.0)	(1,480.0)
Dividends, Cash [Abstract]
Equity, Ending Balance	(5,731.0)	1,290.0
Treasury Stock
Common Stock [Abstract]
Equity, Beginning Balance	(15,112.0)	(14,205.0)
Dividends, Cash [Abstract]
Treasury stock activity	(1,234.0)	59.0
Equity, Ending Balance	(16,346.0)	(14,146.0)
Non- controlling Interests
Common Stock [Abstract]
Equity, Beginning Balance	31.0	31.0
Net income	21.0	10.0
Dividends, Cash [Abstract]
Other	(17.0)	(11.0)
Equity, Ending Balance	$ 35.0	$ 30.0