Debt (Scheduled Remaining Maturity of Long-term Debt) (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Long-term debt, maturities, repayments of remainder of fiscal year	$ 3,645
Long-term debt, maturities, repayments of principal in next 12 months	4,316
Long-term debt, maturities, repayments of principal in year two	1,801
Long-term debt, maturities, repayments of principal in year three	1,799
Long-term debt, maturities, repayments of principal in year four	985
Long-term debt, maturities, repayments of principal after year five	4,465
Total long-term debt	17,011	$ 17,570
Unsecured debt
Debt Instrument [Line Items]
Long-term debt, maturities, repayments of remainder of fiscal year	1,425
Long-term debt, maturities, repayments of principal in next 12 months	2,409
Long-term debt, maturities, repayments of principal in year two	70
Long-term debt, maturities, repayments of principal in year three	1,442
Long-term debt, maturities, repayments of principal in year four	760
Long-term debt, maturities, repayments of principal after year five	4,456
Total long-term debt	10,562	10,424
Secured debt
Debt Instrument [Line Items]
Total long-term debt	6,449	$ 7,146
Long-term debt | Unsecured debt
Debt Instrument [Line Items]
Long-term debt, maturities, repayments of remainder of fiscal year	1,477
Long-term debt, maturities, repayments of principal in next 12 months	2,483
Long-term debt, maturities, repayments of principal in year two	152
Long-term debt, maturities, repayments of principal in year three	1,536
Long-term debt, maturities, repayments of principal in year four	867
Long-term debt, maturities, repayments of principal after year five	4,861
Total long-term debt	11,376
Long-term debt | Secured debt
Debt Instrument [Line Items]
Long-term debt, maturities, repayments of remainder of fiscal year	2,220
Long-term debt, maturities, repayments of principal in next 12 months	1,907
Long-term debt, maturities, repayments of principal in year two	1,731
Long-term debt, maturities, repayments of principal in year three	357
Long-term debt, maturities, repayments of principal in year four	225
Long-term debt, maturities, repayments of principal after year five	9
Total long-term debt	6,449
Original issue discount | Unsecured debt
Debt Instrument [Line Items]
Debt instrument, unamortized discount	(814)
Original issue discount | Unsecured debt | 2024
Debt Instrument [Line Items]
Debt instrument, unamortized discount, current	(52)
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	$ (405)