Debt (Long-term Debt) (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Long-term debt, due within one year	$ 5,971	$ 4,418
Long-term debt, due after one year	14,125	13,344
Long-term debt	20,096	17,762
Secured debt	11,690	10,124
Unsecured debt
Debt Instrument [Line Items]
Long-term debt, due within one year	2,622	2,023
Long-term debt, due after one year	8,194	8,014
Long-term debt	10,816	10,037
Secured debt
Debt Instrument [Line Items]
Long-term debt, due within one year	3,349	2,395
Long-term debt, due after one year	5,931	5,330
Long-term debt	9,280	7,725
Federal Home Loan Bank advances
Debt Instrument [Line Items]
Secured debt	$ 6,200	$ 5,300