Amount of amortization expense attributable to debt discount (premium) and debt issuance costs.

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

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DEBT - Summary of Interest Expense of Convertible Notes (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Aug. 13, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Debt Instrument [Line Items]
Amortization of debt discount and debt issuance costs				$ 18,090	$ 16,298
2.50% Convertible Notes due 2021 \| Convertible debt
Debt Instrument [Line Items]
Stated coupon interest		$ 1,490	$ 2,156	5,802	6,468
Amortization of debt discount and debt issuance costs	$ 26,100	3,499	4,604	13,252	13,551
Total interest expense 2021 Notes		4,989	$ 6,760	19,054	$ 20,019
5.00% Convertible Notes due 2024 \| Convertible debt
Debt Instrument [Line Items]
Stated coupon interest		750		750
Amortization of debt discount and debt issuance costs		837		837
Total interest expense 2021 Notes		$ 1,587		$ 1,587