Equity-Based Compensation - Summary of Outstanding and Exercisable Options and SARs (Detail) (USD $)	12 Months Ended
Dec. 31, 2014
Stock Option [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Aggregate intrinsic value, Outstanding	$ 12,882,000
Aggregate intrinsic value, Exercisable	12,882,000
Weighted-average remaining contractual term, Outstanding	2 years 2 months 12 days
Weighted-average remaining contractual term, Exercisable	2 years 2 months 12 days
Stock Appreciation Rights (SARs) [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Aggregate intrinsic value, Outstanding	38,061,000
Aggregate intrinsic value, Exercisable	$ 22,354,000
Weighted-average remaining contractual term, Outstanding	7 years
Weighted-average remaining contractual term, Exercisable	6 years

Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

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

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- Definition

Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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- Definition

Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ 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 (e)(1)

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

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