Debt (Recourse Debt Net Principal Amounts Due Over Five Years) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Debt Details [Line Items]
Recourse Debt Total	$ 3,396	$ 3,655
Unamortized (discounts)/premiums & debt issuance (costs)
Debt Details [Line Items]
Recourse Debt Total	(22)
Parent Company [Member]
Debt Details [Line Items]
Recourse Debt Total	3,396
Parent Company [Member] | Debt Maturity Year One [Member]
Debt Details [Line Items]
Recourse Debt Total	5
Parent Company [Member] | Debt Maturity Year Two [Member]
Debt Details [Line Items]
Recourse Debt Total	505
Parent Company [Member] | Debt Maturity Year Three [Member]
Debt Details [Line Items]
Recourse Debt Total	8
Parent Company [Member] | Debt Maturity Year Four [Member]
Debt Details [Line Items]
Recourse Debt Total	1,113
Parent Company [Member] | Debt Maturity Year Five [Member]
Debt Details [Line Items]
Recourse Debt Total	243
Parent Company [Member] | Thereafter
Debt Details [Line Items]
Recourse Debt Total	1,544
Parent Company [Member] | Unamortized (discounts)/premiums & debt issuance (costs)
Debt Details [Line Items]
Recourse Debt Total	$ (22)	$ (31)