FAIR VALUE MEASUREMENTS AND FINANCIAL INSTRUMENTS - Fair Value Measurements, Recurring and Nonrecurring (Details) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Assets:
Cash and cash equivalents	$ 36,492,000	$ 58,263,000
Restricted cash	4,275,000	3,833,000
Long-term receivable	0	2,531,000
Level 1 \| Fair Value, Measurements, Recurring
Assets:
Cash and cash equivalents	36,492,000	58,263,000
Restricted cash	4,275,000	3,833,000
Long-term receivable	0	0
Level 2 \| Fair Value, Measurements, Recurring
Assets:
Cash and cash equivalents	0	0
Restricted cash	0	0
Long-term receivable	0	0
Level 3 \| Fair Value, Measurements, Recurring
Assets:
Cash and cash equivalents	0	0
Restricted cash	0	0
Long-term receivable	0	2,531,000
Credit Facility
Liabilities:
Convertible debt payable to related parties	20,000,000	0
Credit Facility \| Level 1 \| Fair Value, Measurements, Recurring
Liabilities:
Convertible debt payable to related parties	0	0
Credit Facility \| Level 2 \| Fair Value, Measurements, Recurring
Liabilities:
Convertible debt payable to related parties	0	0
Credit Facility \| Level 3 \| Fair Value, Measurements, Recurring
Liabilities:
Convertible debt payable to related parties	20,000,000	0
Senior secured term loan
Liabilities:
Convertible debt payable to related parties	247,204,000	247,204,000
Senior secured term loan \| Level 1 \| Fair Value, Measurements, Recurring
Liabilities:
Convertible debt payable to related parties	0	0
Senior secured term loan \| Level 2 \| Fair Value, Measurements, Recurring
Liabilities:
Convertible debt payable to related parties	204,562,000	201,472,000
Senior secured term loan \| Level 3 \| Fair Value, Measurements, Recurring
Liabilities:
Convertible debt payable to related parties	0	0
Convertible debt payable to related parties
Liabilities:
Convertible debt payable to related parties	1,337,000	0
Convertible debt payable to related parties \| Level 1 \| Fair Value, Measurements, Recurring
Liabilities:
Convertible debt payable to related parties	0	0
Convertible debt payable to related parties \| Level 2 \| Fair Value, Measurements, Recurring
Liabilities:
Convertible debt payable to related parties	0	0
Convertible debt payable to related parties \| Level 3 \| Fair Value, Measurements, Recurring
Liabilities:
Convertible debt payable to related parties	$ 1,337,000	$ 0

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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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.

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Amount, before allowance for credit loss, of financing receivable, classified as noncurrent.

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Amount of cash and cash equivalents restricted as to withdrawal or usage, classified as noncurrent. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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