Debt (Letter of Credit) (Details) - USD ($) $ in Millions		Sep. 30, 2016	Dec. 31, 2015
Line of Credit Facility [Line Items]
Letters of Credit Outstanding, Amount		$ 761	$ 755
Corporate Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Letters of Credit Outstanding, Amount	[1]	268	316
CDH [Member]
Line of Credit Facility [Line Items]
Letters of Credit Outstanding, Amount		261	241
Various Project Financing Facilities [Member]
Line of Credit Facility [Line Items]
Letters of Credit Outstanding, Amount		$ 232	$ 198

[1] The Corporate Revolving Facility represents our primary revolving facility.