Fair Value Measurements Asset Retirement Obligations (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011
Fair Value Disclosures [Abstract]
Asset Retirement Obligation, Liabilities Incurred	$ 13.0
Asset Retirement Obligations Term	50

A general description of the asset retirement obligations and the associated long-lived assets. Description may include the terms of the legal restriction.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 143

-Paragraph 22

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 410

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849

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