FAIR VALUE MEASUREMENTS - Change in Investment in Privately Held Companies (Details) - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Convertible debt fair value	$ 726,200		$ 706,500
Privately held investment
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	8,345	$ 4,871
New investments	500	1,769
Sales of investments	(400)	(1,424)
Changes in foreign exchange rates	14	(50)
Changes in fair value included in other income	100	1,374
Changes in fair value included in other comprehensive income	1,220	100
Ending balance	$ 9,779	$ 6,640

Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Changes in Foreign Exchange Rates

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- Definition

Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Fair Value Adjustment Included in Other Comprehensive Income (Loss)

+ References

No definition available.

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Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Fair Value Adjustment Included in Other Income

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- Definition

Fair value portion of borrowing which can be exchanged for a specified number of another security at the option of the issuer or the holder, for example, but not limited to, the entity's common stock.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

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- Definition

Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

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- Definition

Amount of sale of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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- Definition

Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

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