DEBT - Schedule of Interest Expense Recognized (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Convertible notes
Debt Instrument [Line Items]
Contractual interest expense	$ 4,313	$ 4,313	$ 8,626	$ 8,626
Accretion of debt discount	1,499	411	1,930	815
Amortization of debt issuance costs	593	632	1,256	1,255
Total	6,405	$ 5,356	$ 11,812	$ 10,696
Line of Credit
Debt Instrument [Line Items]
Contractual interest expense	10,298
Accretion of debt discount	699
Amortization of debt issuance costs	663
Total	$ 11,660

Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense.

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Amount of amortization expense attributable to debt issuance costs.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of the cost of borrowed funds accounted for as interest expense for debt.

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Represents the portion of interest incurred in the period on debt arrangements that was charged against earnings, excluding amortization of debt discount (premium) and financing costs.

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