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Debt (Details) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Dec. 31, 2017
Carrying value of convertible notes [Abstract]      
Discount $ 696 $ 0  
Carrying value $ 39,084   $ 0
2021 Convertible Notes [Member]      
Debt Instrument [Line Items]      
Debt instrument maturity date Aug. 01, 2021    
Convertible senior notes, interest rate, stated percentage 5.75%    
Debt conversion ratio 31.1876    
Conversion price (in dollars per share) $ 1    
Percentage of common stock conversion price 200.00%    
Number of trading days immediately preceding notice of redemption 5 days    
Redemption price percentage 100.00%    
Percentage of convertible notes due and payable in event of default 100.00%    
Debt instrument, additional interest in the event of default for first 90 Days 0.25%    
Debt instrument, additional interest in the event of default between 91st Day to 180th Day 0.50%    
Effective interest rate 15.30%    
Fair value convertible note $ 38,388    
Carrying value of convertible notes [Abstract]      
Principal amount 52,000    
Discount (12,916)    
Carrying value $ 39,084    
2021 Convertible Notes [Member] | Minimum [Member]      
Debt Instrument [Line Items]      
Debt conversion ratio 0    
Stock price considered for conversion rate (in dollars per share) $ 26.72    
Percentage holders of principal amount of debt 25.00%    
2021 Convertible Notes [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt conversion ratio 6.2375    
Stock price considered for conversion rate (in dollars per share) $ 160.00