Debt (Long-term Debt) (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Long-term debt, due within one year	$ 4,340,000,000	$ 4,418,000,000
Long-term debt, due after one year	13,230,000,000	13,344,000,000
Long-term debt	17,570,000,000	17,762,000,000
Interest Rate Swap
Debt Instrument [Line Items]
Total derivative contracts in a payable position	0	2,500,000,000
Unsecured debt
Debt Instrument [Line Items]
Long-term debt, due within one year	1,409,000,000	2,023,000,000
Long-term debt, due after one year	9,015,000,000	8,014,000,000
Long-term debt	10,424,000,000	10,037,000,000
Secured debt
Debt Instrument [Line Items]
Long-term debt, due within one year	2,931,000,000	2,395,000,000
Long-term debt, due after one year	4,215,000,000	5,330,000,000
Long-term debt	$ 7,146,000,000	$ 7,725,000,000