Equity-Based Compensation - Summary of Total Unrecognized Compensation Expense and Remaining Weighted Average Recognition Period Related to Outstanding Equity-Based Awards (Detail) $ in Thousands	9 Months Ended
Sep. 30, 2018 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining weighted average recognition period	4 months 24 days
Unrecognized compensation expense related to outstanding options	$ 360
Total unrecognized compensation expense at September 30, 2018	$ 18,432
RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining weighted average recognition period	1 year 9 months 18 days
Unrecognized compensation expense related to outstanding equity-based awards other than options	$ 11,895
PSAs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining weighted average recognition period	1 year 4 months 24 days
Unrecognized compensation expense related to outstanding equity-based awards other than options	$ 3,834
RSAs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining weighted average recognition period	1 year 4 months 24 days
Unrecognized compensation expense related to outstanding equity-based awards other than options	$ 2,343

Unrecognized cost of unvested share-based compensation awards.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

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- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

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Unrecognized cost of unvested options awarded to employees as compensation.

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- Definition

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