CONVERTIBLE NOTES AND OTHER DEBTS - Interest (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Convertible Note due 2022
Debt Instrument [Line Items]
Contractual interest expense	$ 1,648	$ 953
Amortization of debt discount	685	373
Amortization of debt issuance costs	214	117
Total interest expense recognized	2,547	1,443
Convertible Note due 2024
Debt Instrument [Line Items]
Contractual interest expense	2,312	2,310
Amortization of debt discount	4,718	4,358
Amortization of debt issuance costs	641	595
Total interest expense recognized	7,671	7,263
Convertible Note due 2020
Debt Instrument [Line Items]
Contractual interest expense	0	936	$ 4,148
Amortization of debt discount	0	1,158	4,787
Amortization of debt issuance costs	0	138	577
Total interest expense recognized	$ 0	$ 2,232	$ 9,512