Debt (Letter of Credit) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013		Dec. 31, 2012
Line of Credit Facility [Line Items]
Letters of Credit Outstanding, Amount	$ 614		$ 626
Corporate Revolving Facility [Member]
Line of Credit Facility [Line Items]
Letters of Credit Outstanding, Amount	240	[1]	243	[1]
CDH [Member]
Line of Credit Facility [Line Items]
Letters of Credit Outstanding, Amount	243		253
Various Project Financing Facilities [Member]
Line of Credit Facility [Line Items]
Letters of Credit Outstanding, Amount	$ 131		$ 130

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