FINANCING ARRANGEMENTS - Schedule of Convertible Debt Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Debt Disclosure [Abstract]
Contractual interest (3.25% of the principal amount per annum)	$ 2,032	$ 2,032	$ 6,096	$ 6,096
Amortization of debt discount	3,016	2,722	8,822	7,964
Total	$ 5,048	$ 4,754	$ 14,918	$ 14,060

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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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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