Variable Interest Entities (Details) (VIE, not primary beneficiary, Corridor Pipeline [Member], USD $) In Millions	3 Months Ended
Sep. 30, 2011
VIE, not primary beneficiary \| Corridor Pipeline [Member]
Variable Interest Entity [Line Items]
Recorded liability related to unconsolidated VIE	$ 3
Maximum exposure to loss related to unconsolidated VIE	$ 696

The carrying amount of the liabilities in the enterprise's statement of financial position that relate to the enterprise's variable interest in the unconsolidated variable interest entity. In general, a VIE is a corporation, partnership, trust, or any other legal structure used for business purposes that either (a) does not have equity investors with voting rights or (b) has equity investors that do not provide sufficient financial resources for the entity to support its activities. A VIE often holds financial assets, including loans or receivables, real estate or other property. A VIE may be essentially passive or it may engage in research and development or other activities on behalf of another company.

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

-Publisher FASB

-Name FASB Interpretation (FIN)

-Number 46R

-Paragraph 23

-Subparagraph b

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

-Publisher FASB

-Name FASB Staff Position (FSP)

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

-Paragraph C6

-Subparagraph a

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Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration