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 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Debt Instrument [Line Items]        
Effective interest rate 10.18% 10.18% 10.18% 10.18%
Contractually stated interest expense $ 1,509 $ 1,505 $ 4,511 $ 4,536
Amortization of discount $ 5,135 $ 4,649 $ 14,934 $ 13,587