STOCK-BASED COMPENSATION - NARRATIVE (Detail) - USD ($)	3 Months Ended
Mar. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of available shares consumed for each restricted stock and restricted stock units issued (in shares)	1.75
Shares available for purchase (in shares)	917,000
Unrecognized compensation cost	$ 7,600,000
Unrecognized compensation cost, recognized over an estimated weighted-average period (years)	2 years 10 months 10 days
Stock options outstanding
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based payment award vesting period (years)	4 years
Stock options outstanding (in shares)	2,268,000
Stock options outstanding \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based payment award expiration period (years)	7 years
Stock options outstanding \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based payment award expiration period (years)	10 years
RSAs outstanding
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based payment award vesting period (years)	1 year
RSUs outstanding
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based payment award vesting period (years)	3 years
Market condition based stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options outstanding (in shares)	272,081	272,081
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of fair market value on the purchase date	85.00%
Maximum number of shares per employee (in shares)	2,000
Employee stock purchase plan offering period	6 months
Maximum value of shares per employee	$ 25,000
Common stock reserved for issuance (in shares)	1,000,000
Purchases under ESPP (in shares)	13,479
Shares available for purchase (in shares)	261,699

The reduction in number of available shares when a share is issued under the share based compensation.

No definition available.

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- Definition

The highest value of shares that an employee can purchase under the plan per period.

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The offering period of the employee stock purchase plan ("ESPP").

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Aggregate number of common shares reserved for future issuance.

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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.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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.

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The highest quantity of shares an employee can purchase under the plan per period.

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- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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- Definition

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

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The number of shares purchased on the open market during the period for issuance to employees under the plan.

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- Definition

Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

Purchase price of common stock expressed as a percentage of its fair value.

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