Debt - Debt Cash Tender Offers and Redemptions (Details) £ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)	Dec. 31, 2023 GBP (£)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Debt Instrument [Line Items]
Repayments of long-term debt	$ 2,304		$ 9,455	$ 4,147
Gain (loss) on extinguishment of debt	37		$ (303)	$ (389)
Certain Notes And Debentures Issued Or Guaranteed
Debt Instrument [Line Items]
Repayments of long-term debt	2,200
Debt redeemed, including accrued and unpaid interest	2,200
Gain (loss) on extinguishment of debt	37
5.00% Notes Due 2023
Debt Instrument [Line Items]
Repayments of long-term debt	$ 388	£ 311
Interest rate (as a percent)	5.00%
Senior Notes Due 2040
Debt Instrument [Line Items]
Interest rate (as a percent)	8.875%
Senior Notes Due 2040 | Senior Notes
Debt Instrument [Line Items]
Debt redeemed, including accrued and unpaid interest	$ 289
Debt redeemed	$ 199
Principal amount redeemed (as a percent)	143.968%	143.968%
Certain Notes And Debentures Issued Or Guaranteed, Tender Offer
Debt Instrument [Line Items]
Repayments of long-term debt	$ 1,600
Debt redeemed, including accrued and unpaid interest	$ 1,500