INDEBTEDNESS - Interest Expense on Convertible Notes (Details) - Convertible Debt - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Debt Instrument [Line Items]
Contractual interest expense	$ 1,373	$ 1,277
Amortization of debt discount and issuance costs	12,528	9,608
Total	$ 13,901	$ 10,885

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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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.

+ References

No definition available.

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

+ References

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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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