Debt - Summary of Retail Deposits (Details) - Germany [Member] - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Outstanding Balance
Overnight deposits	$ 788	$ 799
Term deposits - 12 months	417	423
Term deposits - 24 months	298	281
Term deposits - 36 months	410	392
Total deposits	$ 1,913	$ 1,895
Weighted Average Interest Rate
Overnight deposits (percent)	0.40%	0.50%
Term deposits -12 months (percent)	0.84%	0.93%
Term deposits - 24 months (percent)	1.24%	1.26%
Term deposits - 36 months (percent)	1.47%	1.48%
Total deposits (percent)	0.86%	0.91%