Variable Interest Entities and Unconsolidated Investments (Details 2) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010
Variable Interest Entities and Unconsolidated Investments (Textuals) [Abstract]
Variable Interest Entity, Financial or Other Support, Amount	$ 171	$ 46
NDH Project Debt Credit Facility [Member]
Variable Interest Entities and Unconsolidated Investments (Textuals) [Abstract]
Variable Interest Entity, Financial or Other Support, Amount		540
York Energy Center [Member]
Variable Interest Entities and Unconsolidated Investments (Textuals) [Abstract]
Variable Interest Entity, Financial or Other Support, Amount		$ 110

The amount of financial or other support the reporting entity has provided (explicitly or implicitly) to the Variable Interest Entity (VIE) that it was not previously contractually required to provide or that the reporting entity intends to provide, including, for example, situations in which the reporting entity assisted the VIE in obtaining another type of support.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 5A

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6970148&loc=SL6759159-111685

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS140-4/FIN46(R)-8

-Paragraph C4

-Subparagraph c

-Clause 1

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Name:	us-gaap_VariableInterestEntityFinancialOrOtherSupportAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration