STOCK-BASED COMPENSATION - SUMMARY OF EQUITY INCENTIVE PROGRAM (Details) - shares	6 Months Ended
Jun. 30, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock shares available for grant (in shares)	0
Standard and market condition-based stock options outstanding (in shares)	375,000
Non-option equity instruments outstanding (in shares)		802,000
2011 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Authorized shares cancelled during period (in shares)	3,708,238
Stock options outstanding
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Standard and market condition-based stock options outstanding (in shares)	375,000	828,000
PSUs outstanding
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-option equity instruments outstanding (in shares)	190,000	250,000
Authorized shares cancelled during period (in shares)	0
RSUs outstanding
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-option equity instruments outstanding (in shares)	364,000
Authorized shares cancelled during period (in shares)	310,000
RSAs outstanding
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-option equity instruments outstanding (in shares)	0	130,000
Authorized shares cancelled during period (in shares)	130,000

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
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-Paragraph 2
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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 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 options outstanding, including both vested and non-vested options.

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