Debt (Long-term Debt) (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Long-term debt, due within one year	$ 4,917	$ 4,418
Long-term debt, due after one year	15,563	13,344
Long-term debt	20,480	17,762
Secured debt	11,286	10,124
Unsecured debt
Debt Instrument [Line Items]
Long-term debt, due within one year	2,015	2,023
Long-term debt, due after one year	8,634	8,014
Long-term debt	10,649	10,037
Secured debt
Debt Instrument [Line Items]
Long-term debt, due within one year	2,902	2,395
Long-term debt, due after one year	6,929	5,330
Long-term debt	9,831	7,725
Federal Home Loan Bank advances
Debt Instrument [Line Items]
Secured debt	$ 6,800	$ 5,300