Capital Structure - Narrative (Details)						12 Months Ended
	Jun. 15, 2023 USD ($)	May 18, 2023 USD ($) $ / shares shares	Apr. 17, 2023 USD ($) $ / shares shares	Mar. 31, 2023 USD ($)	Mar. 29, 2023 USD ($)	Dec. 31, 2023 USD ($) director $ / shares shares	Dec. 31, 2022 USD ($) $ / shares shares	Dec. 31, 2021 USD ($)	Nov. 30, 2020 USD ($)
Class of Stock [Line Items]
Debt outstanding						$ 7,942,000,000	$ 7,964,000,000
Additional borrowing capacity under credit facility increase provision						$ 500,000,000
Maximum debt to capital ratio allowed under credit facility covenant (as a percent)						37.50%
Credit facility, amount outstanding						$ 0	0
Interest paid on debt						355,000,000	323,000,000	$ 321,000,000
Other liabilities and accrued expenses						$ 209,000,000	$ 371,000,000
Common stock
Common stock, shares, issued (in shares) | shares						900,000,000	900,000,000
Common stock, shares, outstanding (in shares) | shares						262,000,000	263,000,000
Treasury stock, shares (in shares) | shares						638,000,000	637,000,000
Reacquired shares (in shares) | shares						3,000,000
Average cost of reacquired shares (in dollars per share) | $ / shares						$ 118.18
Reissued net shares under equity incentive plans (in shares) | shares						2,000,000
Preferred stock
Preferred stock, par or stated value per share (in dollars per share) | $ / shares						$ 1	$ 1
Redemption of preferred stock			$ 575,000,000
Preferred stock, shares issued (in shares) | shares						82,000	81,000
Proceeds from issuance of preferred stock, gross						$ 2,050,000,000	$ 2,025,000,000
Noncumulative Perpetual Preferred Stock
Class of Stock [Line Items]
Period after occurrence of certain tax and rating agency events in which redemption of debt in whole permissible						90 days
Preferred stock
Preferred stock, par or stated value per share (in dollars per share) | $ / shares						$ 1.00
Preferred stock, shares liquidation preference (in dollars per share) | $ / shares						25,000
Preferred stock, redemption price (in dollars per share) | $ / shares						$ 25,000
Series G (2)
Preferred stock
Preferred stock, par or stated value per share (in dollars per share) | $ / shares			$ 1.00
Preferred stock, shares liquidation preference (in dollars per share) | $ / shares			$ 25,000
Stock redeemed (in shares) | shares			23,000
Preferred stock dividends			$ 18,000,000
Preferred stock, shares issued (in shares) | shares						0	23,000
Proceeds from issuance of preferred stock, gross						$ 0	$ 575,000,000.0
Series J
Preferred stock
Preferred stock, par or stated value per share (in dollars per share) | $ / shares		$ 1.00
Preferred stock, shares liquidation preference (in dollars per share) | $ / shares		$ 25,000
Preferred stock, shares issued (in shares) | shares		24,000				24,000	0
Proceeds from issuance of preferred stock, gross		$ 600,000,000				$ 600,000,000.0	$ 0
Maximum | Noncumulative Perpetual Preferred Stock
Preferred stock
Additional members of the board of directors | director						2
Preferred stock, redemption price (in dollars per share) | $ / shares						$ 25,500
Minimum | Noncumulative Perpetual Preferred Stock
Preferred stock
Preferred stock, redemption price (in dollars per share) | $ / shares						$ 25,000
Commercial Paper
Class of Stock [Line Items]
Commercial Paper maximum borrowing capacity									$ 750,000,000
Amount of commercial paper outstanding						$ 0	$ 0
5.100% Subordinated Debentures, due 2053
Class of Stock [Line Items]
Stated interest rate (as a percent)						5.10%
Debt outstanding						$ 500,000,000
5.100% Subordinated Debentures, due 2053 | London Interbank Offered Rate
Class of Stock [Line Items]
Interest rate spread over LIBOR (as a percent)						3.165%
5.100% Subordinated Debentures, due 2053 | Secured Overnight Financing Rate (SOFR) | Maximum
Class of Stock [Line Items]
Interest rate spread over LIBOR (as a percent)						3.165%
5.100% Subordinated Debentures, due 2053 | Secured Overnight Financing Rate (SOFR) | Minimum
Class of Stock [Line Items]
Interest rate spread over LIBOR (as a percent)						0.26161%
5.750% Subordinated Debentures, due 2053
Class of Stock [Line Items]
Stated interest rate (as a percent)						5.75%
Debt outstanding						$ 800,000,000
5.750% Subordinated Debentures, due 2053 | London Interbank Offered Rate
Class of Stock [Line Items]
Interest rate spread over LIBOR (as a percent)						2.938%
5.750% Subordinated Debentures, due 2053 | Secured Overnight Financing Rate (SOFR) | Maximum
Class of Stock [Line Items]
Interest rate spread over LIBOR (as a percent)						2.938%
5.750% Subordinated Debentures, due 2053 | Secured Overnight Financing Rate (SOFR) | Minimum
Class of Stock [Line Items]
Interest rate spread over LIBOR (as a percent)						0.26161%
Subordinated Debentures
Class of Stock [Line Items]
Minimum principal outstanding amount for redemption of debt in whole or in part						$ 25,000,000
Period after occurrence of certain tax and rating agency events in which redemption of debt in whole permissible						90 days
Subordinated Debentures | Secured Overnight Financing Rate (SOFR)
Class of Stock [Line Items]
Interest rate spread over LIBOR (as a percent)						0.26161%
6.500% Junior Subordinated Debentures, due 2067
Class of Stock [Line Items]
Stated interest rate (as a percent)						6.50%
Debt outstanding						$ 500,000,000
6.500% Junior Subordinated Debentures, due 2067 | London Interbank Offered Rate
Class of Stock [Line Items]
Interest rate spread over LIBOR (as a percent)						2.12%
6.500% Junior Subordinated Debentures, due 2067 | Secured Overnight Financing Rate (SOFR)
Class of Stock [Line Items]
Interest rate spread over LIBOR (as a percent)						0.26161%
Debentures
Class of Stock [Line Items]
Maximum period for deferment of interest payment						10 years
Reserved common stock authorized and unissued for debentures obligations (in shares) | shares						75,000,000
7.45% Senior Notes, due 2019
Class of Stock [Line Items]
Threshold percentage of repurchase or redemption of outstanding principal debentures for non applicability of promises and covenants contained in the new RCC						10.00%
Period within which threshold percentage of outstanding principal of debentures is to be purchased for non applicability of promises and covenants contained in the new RCC						1 year
Specified period within which percentage of outstanding principal of debentures is to be purchased for non applicability of promises and covenants contained in the new RCC						10 years
7.45% Senior Notes, due 2019 | Maximum
Class of Stock [Line Items]
Percentage of repurchase or redemption of outstanding principal debentures within specified period for non applicability of promises and covenants contained in the new RCC						25.00%
Senior Notes
Class of Stock [Line Items]
Repayments of senior debt	$ 500,000,000			$ 500,000,000	$ 250,000,000
Senior Notes | Senior Notes Due 2033 at 5.25 Percent
Class of Stock [Line Items]
Debt instrument, face amount				$ 750,000,000
Stated interest rate (as a percent)				5.25%
Senior Notes | London Interbank Offered Rate
Class of Stock [Line Items]
Interest rate spread over LIBOR (as a percent)	3.15%				0.63%
Floating Rate Subordinated Debentures, due 2053
Class of Stock [Line Items]
Debt instrument, face amount						$ 800,000,000