Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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The price per share of the conversion feature embedded in the debt instrument.

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Minimum percentage of common stock price to conversion price of convertible debt instruments to determine eligibility of conversion.

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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, after accumulated amortization, of debt discount.

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Carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion. Senior note holders are paid off in full before any payments are made to junior note holders.

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The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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DEBT - Summary of Liability Component of Convertible Notes (Details) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended
	Aug. 13, 2019	Sep. 09, 2014	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Total			$ 76,443	$ 158,309
Convertible debt
Debt Instrument [Line Items]
Principal amount of the 2021 Notes			145,000	345,000
Unamortized discount of the liability component			(14,963)	(54,521)
Unamortized debt issuance costs			(725)	(2,681)
Total			129,312	$ 287,798
Convertible Senior Notes, 5.0% \| Convertible debt
Debt Instrument [Line Items]
Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger	150.00%
Principal amount of the 2021 Notes			120,000
Unamortized discount of the liability component	$ (54,200)		(51,701)
Unamortized debt issuance costs			(2,796)
Total			$ 65,503
Conversion price (in dollars per share)	$ 3.09
Convertible Senior Notes, 2.5% \| Convertible debt
Debt Instrument [Line Items]
Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger		130.00%	130.00%
Unamortized discount of the liability component		$ (119,000)
Conversion price (in dollars per share)		$ 19.24	$ 19.24