Debt - Summary of Retail Deposits (Details) - Germany [Member] $ in Millions	Dec. 31, 2015 USD ($)
Outstanding Balance
Overnight deposits	$ 555
Term deposits -12 months	337
Term deposits - 24 months	123
Term deposits - 36 months	245
Total deposits	$ 1,260
Weighted Average Interest Rate
Overnight deposits (percent)	1.00%
Term deposits - 12 months (percent)	1.32%
Term deposits - 24 months (percent)	1.44%
Term deposits - 36 months (percent)	1.65%
Total deposits (percent)	1.25%