STOCK-BASED COMPENSATION - 2012 Plan and ESPP (Details)	12 Months Ended
Dec. 31, 2017 USD ($) item shares
2012 Equity Incentive Plan
Stock-based compensation
Shares remaining available for issuance	3,411,107
ESPP \| Employee Stock
Stock-based compensation
Purchase price as a percentage of fair market value of stock	85.00%
Total duration of consecutive and overlapping offering periods	24 months
Number of offering periods \| item	4
Duration of purchase period	6 months
Maximum contributions as a percentage of employee's eligible compensation	15.00%
Maximum number of shares an employee may purchase during any purchase period	2,500
Maximum value of shares an employee may purchase in a calendar year \| $	$ 25,000
Shares remaining available for issuance	205,979

Represents the consecutive and overlapping offering period for the offering of share-based payment awards.

No definition available.

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- Definition

Maximum amount the employee may contribute of employee's eligible compensation.

+ References

No definition available.

+ Details

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- Definition

Represents the number of purchase periods having duration of six months each.

+ References

No definition available.

+ Details

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- Definition

Represents the duration of each purchase period within each consecutive and overlapping purchase period for offering of share-based payment awards.

+ References

No definition available.

+ Details

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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.

+ Details

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- Definition

The highest percentage of annual salary that an employee is permitted to utilize with respect to the plan.

+ References

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=96867065&loc=d3e5070-113901

+ Details

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Period Type:	instant

- Definition

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

+ References

+ Details

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Balance Type:	na
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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.

+ References

+ Details

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- Definition

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

+ References

No definition available.

+ Details

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- Details

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- Details

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