FINANCIAL INSTRUMENTS - Carrying Value and Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Current portion of long-term debt—related party	$ 0	$ (816)
Long-term debt—related party, net	(1,048)	(1,997)
Carrying value
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Current portion of long term debt	(13,750)	(13,750)
Long-term debt, net	(248,455)	(258,312)
Current portion of long-term debt—related party	0	(816)
Long-term debt—related party, net	(1,048)	(1,997)
Unamortized debt issuance costs	(2,500)	(2,900)
Fair value
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Current portion of long term debt	(13,664)	(13,802)
Long-term debt, net	(249,369)	(262,230)
Current portion of long-term debt—related party	0	(837)
Long-term debt—related party, net	$ (1,155)	$ (2,048)

Amount of unamortized debt discount (premium) and debt issuance costs.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 30
-Section 45
-Paragraph 3
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- Definition

Carrying amount as of the balance sheet date of obligations due all related parties. For classified balance sheets, represents the current portion of such liabilities (due within one year or within the normal operating cycle if longer).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
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-Publisher FASB
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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-Section S99
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Portion of the carrying amount as of the balance sheet date of obligations due all related parties that is payable after one year or beyond the normal operating cycle if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section S99
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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 fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

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This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents the amount of short-term debt existing as of the balance sheet date.

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