STOCK PLANS - Stock Incentive Plans (Details)	12 Months Ended
Dec. 31, 2021 shares
Stock Incentive Plans
Stock incentive plan, awards reserved for issuance (in shares)	14,606,701
Stock incentive plan, awards issued (in shares)	12,461,531
Stock incentive plan, awards available for grant (in shares)	2,145,170
2011 Plan
Stock Incentive Plans
Stock incentive plan, awards reserved for issuance (in shares)	14,431,701
Stock incentive plan, awards issued (in shares)	12,425,455
Stock incentive plan, awards available for grant (in shares)	2,006,246
2014 Inducement Plan
Stock Incentive Plans
Stock incentive plan, awards reserved for issuance (in shares)	175,000
Stock incentive plan, awards issued (in shares)	36,076
Stock incentive plan, awards available for grant (in shares)	138,924
2014 ESPP
Stock Incentive Plans
ESPP, shares reserved for purchase (in shares)	500,000
ESPP, shares purchased (in shares)	409,049
ESPP, shares available for purchase (in shares)	90,951

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Number of shares authorized for issuance under share-based payment arrangement.

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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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Number of shares issued under share-based payment arrangement.

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Number of shares issued during the period as a result of an employee stock purchase plan.

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