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Llitigation (Details) - USD ($)	Dec. 31, 2015	Mar. 12, 2015	Dec. 31, 2014	Aug. 31, 2011	Oct. 31, 2010
Loss Contingencies [Line Items]
Potential liabilities related to litigation and environmental matters	$ 19,500,000		$ 27,600,000
Natural gas gathering operations [Member]
Loss Contingencies [Line Items]
Arbitration award					$ 26,600,000
Litigation related to construction materials [Member]
Loss Contingencies [Line Items]
Loss contingency, estimate of possible loss				$ 3,700,000
Additional amount per day of potential penalties				$ 5,000
Litigation Related To Construction Services [Member]
Loss Contingencies [Line Items]
Damage Repair Estimate		$ 21,000,000

X

- Definition

Additional amount per day of potential penalties.

+ References

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- Definition

Arbitration award.

+ References

No definition available.

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- Definition

Damage repair estimate for alleged defects.

+ References

No definition available.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Amount of loss contingency liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349

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- Definition

Reflects the estimated amount of loss from the specified contingency as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 9
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14557-108349

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