Debt (Scheduled Remaining Maturity of Long-term Debt) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Long-term debt, maturities, repayments of principal in next 12 months	$ 4,340
Long-term debt, maturities, repayments of principal in year two	4,315
Long-term debt, maturities, repayments of principal in year three	1,790
Long-term debt, maturities, repayments of principal in year four	1,799
Long-term debt, maturities, repayments of principal in year five	985
Long-term debt, maturities, repayments of principal after year five	4,341
Total long-term debt	17,570	$ 17,762
Unsecured debt
Debt Instrument [Line Items]
Long-term debt, maturities, repayments of principal in next 12 months	1,409
Long-term debt, maturities, repayments of principal in year two	2,411
Long-term debt, maturities, repayments of principal in year three	70
Long-term debt, maturities, repayments of principal in year four	1,442
Long-term debt, maturities, repayments of principal in year five	760
Long-term debt, maturities, repayments of principal after year five	4,332
Total long-term debt	10,424	10,037
Secured debt
Debt Instrument [Line Items]
Total long-term debt	7,146	$ 7,725
Long-term debt | Unsecured debt
Debt Instrument [Line Items]
Long-term debt, maturities, repayments of principal in next 12 months	1,477
Long-term debt, maturities, repayments of principal in year two	2,485
Long-term debt, maturities, repayments of principal in year three	152
Long-term debt, maturities, repayments of principal in year four	1,536
Long-term debt, maturities, repayments of principal in year five	867
Long-term debt, maturities, repayments of principal after year five	4,738
Total long-term debt	11,255
Long-term debt | Secured debt
Debt Instrument [Line Items]
Long-term debt, maturities, repayments of principal in next 12 months	2,931
Long-term debt, maturities, repayments of principal in year two	1,904
Long-term debt, maturities, repayments of principal in year three	1,720
Long-term debt, maturities, repayments of principal in year four	357
Long-term debt, maturities, repayments of principal in year five	225
Long-term debt, maturities, repayments of principal after year five	9
Total long-term debt	7,146
Original issue discount | Unsecured debt
Debt Instrument [Line Items]
Debt instrument, unamortized discount	(831)
Original issue discount | Unsecured debt | 2024
Debt Instrument [Line Items]
Debt instrument, unamortized discount, current	(68)
Original issue discount | Unsecured debt | 2025
Debt Instrument [Line Items]
Debt instrument, unamortized discount, noncurrent	(74)
Original issue discount | Unsecured debt | 2026
Debt Instrument [Line Items]
Debt instrument, unamortized discount, noncurrent	(82)
Original issue discount | Unsecured debt | 2027
Debt Instrument [Line Items]
Debt instrument, unamortized discount, noncurrent	(94)
Original issue discount | Unsecured debt | 2028
Debt Instrument [Line Items]
Debt instrument, unamortized discount, noncurrent	(107)
Original issue discount | Unsecured debt | 2029 and thereafter
Debt Instrument [Line Items]
Debt instrument, unamortized discount, noncurrent	$ (406)