Debt (Recourse Debt Net Principal Amounts Due Over Five Years) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Debt Details [Line Items]
Recourse Debt Total	$ 3,447	$ 3,396
Debt Maturity Year One [Member]
Debt Details [Line Items]
Recourse Debt Total	1
Debt Maturity Year Two [Member]
Debt Details [Line Items]
Recourse Debt Total	3
Debt Maturity Year Three [Member]
Debt Details [Line Items]
Recourse Debt Total	3
Debt Maturity Year Four [Member]
Debt Details [Line Items]
Recourse Debt Total	74
Debt Maturity Year Five [Member]
Debt Details [Line Items]
Recourse Debt Total	903
Thereafter
Debt Details [Line Items]
Recourse Debt Total	2,504
Unamortized (discounts)/premiums & debt issuance (costs)
Debt Details [Line Items]
Recourse Debt Total	$ (41)