STOCK BASED COMPENSATION - Summary of Stock Option Plan (Detail)	6 Months Ended
Jun. 30, 2018 $ / shares shares
Shares
Outstanding, Beginning balance (in shares) \| shares	2,854,213
Granted (in shares) \| shares	721,762
Exercised (in shares) \| shares	(98,270)
Canceled/Forfeited (in shares) \| shares	(194,849)
Outstanding, Ending balance (in shares) \| shares	3,282,856
Options exercisable (in shares) \| shares	1,541,557
Weighted Average Exercise Price Per Share
Outstanding, Beginning balance (usd per share) \| $ / shares	$ 17.50
Granted (usd per share) \| $ / shares	23.86
Exercised (usd per share) \| $ / shares	16.16
Canceled/Forfeited (usd per share) \| $ / shares	18.52
Outstanding, Ending balance (usd per share) \| $ / shares	18.86
Options exercisable (usd per share) \| $ / shares	$ 18.74

The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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Gross number of share options (or share units) granted during the period.

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Number of options outstanding, including both vested and non-vested options.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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- Definition

Number of fully vested and expected to vest exercisable options that may be converted into shares under option plan. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted-average exercise price, at which grantee can acquire shares reserved for issuance, for fully vested and expected to vest exercisable or convertible options. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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- Definition

Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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

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