FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
Sep. 30, 2021 USD ($) $ / shares	Sep. 30, 2021 USD ($) $ / shares	Dec. 31, 2020 USD ($)
Fair Value Asset Transfers [Abstract]
Transfers from Level 1 to Level 2	$ 0	$ 0	$ 0
Transfers from Level 2 to Level 1	0	0	0
Transfers into Level 3	0	0	0
Transfers out of Level 3	0	0	0
Fair Value Liability Transfers [Abstract]
Transfers from Level 1 to Level 2	0	0	0
Transfers from Level 2 to Level 1	0	0	0
Transfers into Level 3	0	0	0
Transfers out of Level 3	0	0	0
Recurring [Member]
Assets [Abstract]
Mutual funds - Cash and cash equivalents	59,896	59,896
Mutual funds - Marketable securities	438,102	438,102
Total assets	497,998	497,998
Liabilities [Abstract]
Total liabilities	8,176	8,176
Recurring [Member] \| Level 1 [Member]
Assets [Abstract]
Mutual funds - Cash and cash equivalents	59,896	59,896	$ 36,040
Mutual funds - Marketable securities	438,102	438,102
Total assets	497,998	497,998
Liabilities [Abstract]
Total liabilities	7,782	7,782
Recurring [Member] \| Level 2 [Member]
Assets [Abstract]
Mutual funds - Cash and cash equivalents	0	0
Mutual funds - Marketable securities	0	0
Total assets	0	0
Liabilities [Abstract]
Total liabilities	0	0
Recurring [Member] \| Level 3 [Member]
Assets [Abstract]
Mutual funds - Cash and cash equivalents	0	0
Mutual funds - Marketable securities	0	0
Total assets	0	0
Liabilities [Abstract]
Total liabilities	394	394
Recurring [Member] \| Private Warrants [Member]
Liabilities [Abstract]
Warrants	394	394
Recurring [Member] \| Private Warrants [Member] \| Level 1 [Member]
Liabilities [Abstract]
Warrants	0	0
Recurring [Member] \| Private Warrants [Member] \| Level 2 [Member]
Liabilities [Abstract]
Warrants	0	0
Recurring [Member] \| Private Warrants [Member] \| Level 3 [Member]
Liabilities [Abstract]
Warrants	394	394
Recurring [Member] \| Public Warrants [Member]
Liabilities [Abstract]
Warrants	7,782	7,782
Recurring [Member] \| Public Warrants [Member] \| Level 1 [Member]
Liabilities [Abstract]
Warrants	7,782	7,782
Recurring [Member] \| Public Warrants [Member] \| Level 2 [Member]
Liabilities [Abstract]
Warrants	0	0
Recurring [Member] \| Public Warrants [Member] \| Level 3 [Member]
Liabilities [Abstract]
Warrants	$ 0	$ 0
Warrants [Member] \| Private Warrants [Member] \| Volatility [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrants measurement input	0.523	0.523
Warrants [Member] \| Private Warrants [Member] \| Risk-Free Interest Rate [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrants measurement input	0.0091	0.0091
Warrants [Member] \| Private Warrants [Member] \| Strike Price [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrants measurement input \| $ / shares	11.50	11.50
Warrants [Member] \| Private Warrants [Member] \| Share Price [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrants measurement input \| $ / shares	8.34	8.34
Warrants [Member] \| Private Warrants [Member] \| Expected Life [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrants term	4 years 8 months 12 days	4 years 8 months 12 days

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Fair value portion 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.

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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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Amount of transfers of assets measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2.

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Amount of transfers of assets measured on a recurring basis out of Level 2 of the fair value hierarchy into Level 1.

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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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Fair value of financial and nonfinancial obligations.

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Value of input used to measure outstanding warrant and right embodying unconditional obligation requiring redemption by transferring asset at specified or determinable date or upon event certain to occur.

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