Debt (Long-term Debt) (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Long-term debt, due within one year	$ 5,156	$ 4,418
Long-term debt, due after one year	14,985	13,344
Long-term debt	20,141	17,762
Secured debt	11,567	10,124
Unsecured debt
Debt Instrument [Line Items]
Long-term debt, due within one year	1,948	2,023
Long-term debt, due after one year	8,820	8,014
Long-term debt	10,768	10,037
Secured debt
Debt Instrument [Line Items]
Long-term debt, due within one year	3,208	2,395
Long-term debt, due after one year	6,165	5,330
Long-term debt	9,373	7,725
Federal Home Loan Bank advances
Debt Instrument [Line Items]
Secured debt	$ 6,700	$ 5,300