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Asset Retirement Obligations - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014 Structure	Dec. 31, 2013
Asset Retirement Obligation Disclosure [Abstract]
Estimated CARO ranges per structure, minimum	$ 1aa_EstimatedCaroRangesPerStructureMinimum
Estimated CARO ranges per structure, maximum	46aa_EstimatedCaroRangesPerStructureMaximum
Number of structures required to demolish	136aa_NumberOfStructuresRequiredToDemolish
Current liability	$ 76us-gaap_AssetRetirementObligationCurrent	$ 85us-gaap_AssetRetirementObligationCurrent

X

- Definition

Estimated CARO ranges per structure maximum.

+ References

No definition available.

+ Details

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X

- Definition

Estimated CARO ranges per structure minimum.

+ References

No definition available.

+ Details

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X

- Definition

Number of structures required to demolish.

+ References

No definition available.

+ Details

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Period Type:	instant

X

- Definition

Current portion of the carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 410

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (c)

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

+ Details

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- Details

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