Debt (Long-term Debt) (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Long-term debt, due within one year	$ 3,574	$ 5,869
Long-term debt, due after one year	13,410	11,160
Long-term debt	16,984	17,029
Secured debt	15,584	7,619
Unsecured debt
Debt Instrument [Line Items]
Long-term debt, due within one year	798	1,028
Long-term debt, due after one year	8,377	8,382
Long-term debt	9,175	9,410
Secured debt
Debt Instrument [Line Items]
Long-term debt, due within one year	2,776	4,841
Long-term debt, due after one year	5,033	2,778
Long-term debt	7,809	7,619
Federal Home Loan Bank advances
Debt Instrument [Line Items]
Secured debt	$ 6,300	$ 6,300