Supplemental Gas and Oil Information - Unaudited Costs Incurred for Cost-of-Service Activities (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Property Acquisition [Abstract]
Unproved	$ 0.3	$ 0.6	$ 0
Proved	106.4	0	0
Development	133.1	146.9	149.1
Total costs incurred for cost-of-service activities	239.8	147.5	149.1
Cost incurred to develop proved undeveloped reserves	$ 106.3	$ 50.4	$ 69.7

Development costs incurred in oil and gas activities of proved undeveloped reserves.

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- Details

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- Definition

Costs incurred, including capitalized costs and costs charged to expense, associated with the acquisition of oil and gas properties that have proved reserves.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 235

-Section 50

-Paragraph 19

-URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62038-109447

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 235

-Section 50

-Paragraph 18

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62014-109447

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- Definition

Costs incurred, including capitalized costs and costs charged to expense, associated with the acquisition of oil and gas properties that have unproved reserves.

+ References

+ Details

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- Definition

Development costs incurred, including capitalized costs and costs charged to expense, in oil and gas activities.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 235

-Section 50

-Paragraph 18

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62014-109447

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- Definition

Amount of costs incurred related to oil and gas property acquisition, exploration and development activities, including capitalized costs and costs charged to expense.

+ References

No definition available.

+ Details

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