Stock-Based Compensation - Additional Information (Detail) shares in Millions, $ in Millions	9 Months Ended
Sep. 30, 2018 USD ($) shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation expense \| $	$ 74.2
Weighted-average period of recognition of unrecognized stock-based compensation expense (in years)	2 years 2 months 12 days
Shares issued \| shares	1.2

Unrecognized cost of unvested share-based compensation awards.

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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.

+ References

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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.

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- Definition

Number of share options (or share units) exercised during the current period.

+ References

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