Total Equity and Other Comprehensive Income (Rollforward of Total Equity) (Details) $ / shares in Units, shares in Thousands, $ in Millions		3 Months Ended
	Feb. 07, 2023 $ / shares shares	Mar. 31, 2024 USD ($) shares	Mar. 31, 2023 USD ($) shares	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Common Stock [Abstract]
Equity, Beginning Balance		$ 51,141.0	$ 45,812.0
Net income		1,344.0	1,694.0
Other comprehensive income (loss), net of tax		(330.0)	1,064.0
Dividends, Cash [Abstract]
Common		(624.0)	(607.0)
Preferred		(81.0)	(68.0)
Preferred stock discount accretion
Preferred stock issuance			1,487.0
Treasury stock activity		1.0	(238.0)
Other		(77.0)	(96.0)
Equity, Ending Balance		51,374.0	49,074.0
Preferred stock, par value		$ 0.5	0.5	$ 0.5	$ 0.5
Cumulative Effect, Period of Adoption, Adjustment
Common Stock [Abstract]
Equity, Beginning Balance			26.0
Cumulative Effect, Period of Adoption, Adjusted Balance
Common Stock [Abstract]
Equity, Beginning Balance			$ 45,838.0
Series W
Dividends, Cash [Abstract]
Depositary shares conversion ratio	0.01
Common stock activity (shares) | shares	1,500
Fixed interest rate	6.25%
Preferred stock, par or stated value per share (in dollars per share) | $ / shares	$ 1
Common Stock
Common Stock [Abstract]
Beginning Balance (in shares) | shares		398,000	401,000
Treasury stock activity, shares | shares			(2,000)
Ending Balance, (in shares) | shares		398,000	399,000
Equity, Beginning Balance		$ 2,716.0	$ 2,714.0
Dividends, Cash [Abstract]
Equity, Ending Balance		2,716.0	$ 2,714.0
Common Stock | Cumulative Effect, Period of Adoption, Adjusted Balance
Common Stock [Abstract]
Beginning Balance (in shares) | shares			401,000
Equity, Beginning Balance			$ 2,714.0
Capital Surplus - Preferred Stock
Common Stock [Abstract]
Equity, Beginning Balance		6,241.0	5,746.0
Dividends, Cash [Abstract]
Preferred stock discount accretion		2.0	2.0
Preferred stock issuance			1,487.0
Equity, Ending Balance		6,243.0	7,235.0
Capital Surplus - Preferred Stock | Cumulative Effect, Period of Adoption, Adjusted Balance
Common Stock [Abstract]
Equity, Beginning Balance			5,746.0
Capital Surplus - Common Stock and Other
Common Stock [Abstract]
Equity, Beginning Balance		12,779.0	12,630.0
Dividends, Cash [Abstract]
Treasury stock activity		71.0	70.0
Other		(61.0)	(71.0)
Equity, Ending Balance		12,789.0	12,629.0
Capital Surplus - Common Stock and Other | Cumulative Effect, Period of Adoption, Adjusted Balance
Common Stock [Abstract]
Equity, Beginning Balance			12,630.0
Retained Earnings
Common Stock [Abstract]
Equity, Beginning Balance		56,290.0	53,572.0
Net income		1,330.0	1,677.0
Dividends, Cash [Abstract]
Common		(624.0)	(607.0)
Preferred		(81.0)	(68.0)
Preferred stock discount accretion		(2.0)	(2.0)
Equity, Ending Balance		56,913.0	54,598.0
Retained Earnings | Cumulative Effect, Period of Adoption, Adjustment
Common Stock [Abstract]
Equity, Beginning Balance			26.0
Retained Earnings | Cumulative Effect, Period of Adoption, Adjusted Balance
Common Stock [Abstract]
Equity, Beginning Balance			53,598.0
Accumulated Other Comprehensive Income (Loss)
Common Stock [Abstract]
Equity, Beginning Balance		(7,712.0)	(10,172.0)
Other comprehensive income (loss), net of tax		(330.0)	1,064.0
Dividends, Cash [Abstract]
Equity, Ending Balance		(8,042.0)	(9,108.0)
Accumulated Other Comprehensive Income (Loss) | Cumulative Effect, Period of Adoption, Adjusted Balance
Common Stock [Abstract]
Equity, Beginning Balance			(10,172.0)
Treasury Stock
Common Stock [Abstract]
Equity, Beginning Balance		(19,209.0)	(18,716.0)
Dividends, Cash [Abstract]
Treasury stock activity		(70.0)	(308.0)
Equity, Ending Balance		(19,279.0)	(19,024.0)
Treasury Stock | Cumulative Effect, Period of Adoption, Adjusted Balance
Common Stock [Abstract]
Equity, Beginning Balance			(18,716.0)
Non- controlling Interests
Common Stock [Abstract]
Equity, Beginning Balance		36.0	38.0
Net income		14.0	17.0
Dividends, Cash [Abstract]
Other		(16.0)	(25.0)
Equity, Ending Balance		$ 34.0	30.0
Non- controlling Interests | Cumulative Effect, Period of Adoption, Adjusted Balance
Common Stock [Abstract]
Equity, Beginning Balance			$ 38.0