STOCK-BASED COMPENSATION - SUMMARY OF EQUITY INCENTIVE PROGRAM (Details) - shares shares in Thousands	Sep. 30, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock shares available for grant (in shares)	3,172
Standard and market condition-based stock options outstanding
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Standard and market condition-based stock options outstanding (in shares)	2,011
RSAs outstanding
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock outstanding (in shares)	91	55
RSUs outstanding
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock outstanding (in shares)	949	1,091

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=116856206&loc=d3e5070-113901

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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.

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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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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