Inventory (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Inventory [Abstract]
Current assets inventory, underground storage	$ 3.7	$ 5.6
Current assets inventory, tubulars & other equipment	39.5	22.5
Other assets non-current inventory, gathering systems pipe	$ 15.8	$ 13.8

Carrying amount as of the balance sheet date of tubulars and other equipment used in the E&P segment, and deemed to be a current asset because it is expected to be used within twelve months or in the normal operating cycle.

No definition available.

+ Details

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- Definition

Carrying amount as of the balance sheet date of natural gas stored underground in depleted gas reservoirs, aquifers, or salt caverns to meet seasonal and peak load demands, and also as insurance against unforeseen supply disruptions, and deemed to be a current asset because it is expected to be used within twelve months or in the normal operating cycle.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.6(a))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 6

-Subparagraph a

-Article 5

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Details

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- Definition

Carrying amount as of the balance sheet date of inventories not expected to be converted to cash, sold or exchanged within the normal operating cycle (such as inventory related to long-term contracts or program rights).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.6(d))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 6

-Subparagraph d

-Article 5

+ Details

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Period Type:	instant