Quarterly report pursuant to Section 13 or 15(d)

Debt Instruments - Summary of the Effective Interest Rate, Contractually Stated Interest Expense and Costs Related to Amortization of Discount for the Notes (Details)

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Debt Instruments - Summary of the Effective Interest Rate, Contractually Stated Interest Expense and Costs Related to Amortization of Discount for the Notes (Details) - Convertible debt - Notes - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Debt Instrument [Line Items]    
Effective interest rate 10.18% 10.18%
Contractually stated interest expense $ 1,509 $ 1,514
Amortization of discount $ 5,397 $ 4,886