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Stockholders' Equity - Summary of Restricted Stock, Restricted Stock Unit and Performance Stock Unit Activity (Parenthetical) (Detail) - Performance Stock Units [Member]	9 Months Ended
	Sep. 30, 2015 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance stock units, percentage of attainment level	100.00%
Performance stock units	0

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- Definition

Additional shares of Class A Common Stock potentially issuable if maximum attainment levels are met.

+ 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.

+ Details

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- Definition

Percentage of vesting of share-based compensation awards.

+ References

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



-Publisher FASB



-Name Accounting Standards Codification



-Topic 718



-SubTopic 10



-Section 50



-Paragraph 2



-Subparagraph (a)(1)



-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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