CONVERTIBLE NOTES AND OTHER DEBTS - Narrative (Details) $ / shares in Units, $ in Thousands, € in Millions			1 Months Ended		3 Months Ended		6 Months Ended	9 Months Ended	12 Months Ended
	Jun. 26, 2020 day	Jun. 02, 2020 USD ($)	Jun. 30, 2020 EUR (€)	Apr. 30, 2020 CHF (SFr)	Sep. 25, 2020 USD ($) $ / shares	Sep. 27, 2019 USD ($)	Jun. 26, 2020 USD ($)	Sep. 25, 2020 USD ($) $ / shares	Dec. 31, 2021 USD ($) day $ / shares	Dec. 31, 2020 USD ($) $ / shares	Dec. 31, 2019 USD ($) day	Jun. 30, 2020 USD ($)	Dec. 19, 2019 USD ($)	Sep. 13, 2019 USD ($)	Dec. 31, 2015 USD ($)
Debt Instrument [Line Items]
Common stock, par value (in dollars per share) | $ / shares									$ 0.001	$ 0.001
Convertible debt, non-current									$ 98,941	$ 129,507
Fair value of 2022 Notes used to settle 2020 Notes									0	44,357	$ 0
Loss on convertible debt extinguishment									0	1,362	5,695
Reclassification from APIC to convertible debt in mezzanine equity									883	0
Repayments of convertible debt									0	7,999	109,603
Relief loans									5,651	6,694
Societe Generale S.A.
Debt Instrument [Line Items]
Stated interest rate (as a percent)												0.51%
Proceeds from loans | €			€ 5
Relief loans									$ 5,700
UBS Switzerland AG
Debt Instrument [Line Items]
Stated interest rate (as a percent)									0.00%
Proceeds from loans | SFr				SFr 500,000
Debt instrument, term				5 years
Revolving Credit Facility | JPMORGAN CHASE BANK N.A.
Debt Instrument [Line Items]
Stated interest rate (as a percent)									2.00%
Line of credit facility, fair value of amount outstanding									$ 0
Revolving Credit Facility | Maximum | JPMORGAN CHASE BANK N.A.
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity													$ 25,000
One Month LIBOR | Revolving Credit Facility | JPMORGAN CHASE BANK N.A.
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)									2.50%
LIBOR for interest period of one, two or three months | Revolving Credit Facility | JPMORGAN CHASE BANK N.A.
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)									3.00%
Loans Backed By French Research And Development Tax Credit Receivables | TVN
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)									1.90%
Convertible Note due 2022
Debt Instrument [Line Items]
Stated interest rate (as a percent)		4.375%
Debt instrument, face amount		$ 37,700							$ 37,707	37,707
Common stock, par value (in dollars per share) | $ / shares									$ 0.001
Debt instrument, convertible, conversion ratio									173.9978
Debt instrument, convertible, conversion price (in dollars per share) | $ / shares									$ 5.75
Convertible debt, non-current									$ 36,824	35,925
Fair value of 2022 Notes used to settle 2020 Notes		44,400								44,400
Carrying amount of equity component of debt instrument		8,300
Convertible debt		36,000
Debt instrument, unamortized discount		$ 1,700							$ 672	1,357
Other significant noncash transaction, value of consideration received							$ 37,700
Convertible Note due 2022 | Stock price greater or equal 130 percent of Note Conversion Price
Debt Instrument [Line Items]
Debt instrument, convertible, threshold trading days | day	20								20
Debt instrument, convertible, threshold consecutive trading days | day	30								30
Threshold of stock price trigger (as a percent)	130.00%								130.00%
Convertible Note due 2022 | Note price less than 98 percent of stock price times conversion rate
Debt Instrument [Line Items]
Debt instrument, convertible, threshold trading days | day	5
Debt instrument, convertible, threshold consecutive trading days | day	5
Threshold of stock price trigger (as a percent)	98.00%
Convertible Note due 2024
Debt Instrument [Line Items]
Stated interest rate (as a percent)														2.00%
Debt instrument, face amount									$ 115,500	115,500				$ 115,500
Common stock, par value (in dollars per share) | $ / shares									$ 0.001
Debt instrument, convertible, conversion ratio									115.5001
Debt instrument, convertible, conversion price (in dollars per share) | $ / shares									$ 8.66
Convertible debt, non-current									$ 98,941	93,582
Carrying amount of equity component of debt instrument					$ 24,900			$ 24,900
Debt instrument, unamortized discount									$ 14,576	19,294
Convertible Note due 2020
Debt Instrument [Line Items]
Stated interest rate (as a percent)															4.00%
Debt instrument, face amount												$ 8,100			$ 128,300
Debt instrument, convertible, conversion ratio								173.9978
Debt instrument, convertible, conversion price (in dollars per share) | $ / shares					$ 5.75			$ 5.75
Carrying amount of equity component of debt instrument															$ 26,100
Debt instrument, repurchase amount					$ 109,600			$ 109,600
Loss on convertible debt extinguishment							800			500
Reclassification from APIC to convertible debt in mezzanine equity											$ 2,400
Other significant noncash transaction, value of consideration received							$ 37,700
Convertible Note due 2020 | Stock price greater or equal 130 percent of Note Conversion Price
Debt Instrument [Line Items]
Debt instrument, convertible, threshold trading days | day											20
Debt instrument, convertible, threshold consecutive trading days | day											30
Threshold of stock price trigger (as a percent)											130.00%
Convertible Note due 2020 | Maximum
Debt Instrument [Line Items]
Debt instrument, face amount											$ 45,800
Convertible Debt | Convertible Note due 2020
Debt Instrument [Line Items]
Loss on convertible debt extinguishment											$ 5,700
Convertible Debt | Long-term Debt | Convertible Note due 2020 | Privately Negotiated Transactions
Debt Instrument [Line Items]
Extinguishment of debt, amount					$ 82,500
Convertible Debt | Additional Paid-in Capital | Convertible Note due 2020 | Privately Negotiated Transactions
Debt Instrument [Line Items]
Extinguishment of debt, amount						$ 27,100
Convertible Debt Settled in Cash and Company's Stocks | Convertible Note due 2020
Debt Instrument [Line Items]
Repayments of convertible debt										7,800
Convertible Debt Settled in Cash | Convertible Note due 2020
Debt Instrument [Line Items]
Repayments of convertible debt										$ 300