Debt (Recourse Debt Net Principal Amounts Due Over Five Years) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Debt Details [Line Items]
Recourse Debt Total	$ 4,671	$ 4,966
2015
Debt Details [Line Items]
Recourse Debt Total	0
2016
Debt Details [Line Items]
Recourse Debt Total	0
2017
Debt Details [Line Items]
Recourse Debt Total	240
2018
Debt Details [Line Items]
Recourse Debt Total	469
2019
Debt Details [Line Items]
Recourse Debt Total	966
Thereafter
Debt Details [Line Items]
Recourse Debt Total	3,041
Unamortized Discounts [Member]
Debt Details [Line Items]
Recourse Debt Total	$ (45)	$ (51)