Annual report pursuant to Section 13 and 15(d)

Convertible Senior Notes (Details)

v3.8.0.1
Convertible Senior Notes (Details)
$ in Thousands
12 Months Ended
Nov. 01, 2017
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Debt Instrument, Redemption [Line Items]      
Proceeds from convertible senior notes   $ 282,185  
Convertible senior notes maturity date   Jan. 15, 2022  
Convertible senior notes conversion ratio   0.0614698  
Reverse stock split, conversion ratio 0.50    
Convertible senior notes   $ 282,827 $ 0
Convertible Debt [Member]      
Debt Instrument, Redemption [Line Items]      
Convertible senior notes aggregate principal amount   $ 287,500  
Convertible senior notes interest rate per annum   6.25%