Quarterly report pursuant to Section 13 or 15(d)

Debt - Convertible Debt (Details)

v3.8.0.1
Debt - Convertible Debt (Details) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2018
Dec. 31, 2017
May 31, 2017
May 23, 2017
Convertible Debt [Abstract]        
Convertible notes payable, net $ 284,046 $ 281,199    
Convertible Senior Notes | Convertible Senior Notes Due November 2022        
Convertible Debt [Abstract]        
Principal amount 345,000 345,000   $ 345,000
Unamortized discount (54,033) (56,557)    
Unamortized debt issuance costs (6,921) (7,244)    
Convertible notes payable, net 284,046 281,199 $ 282,500  
Equity component 61,390 $ 61,390 $ 62,500  
Interest Expense, Debt [Abstract]        
Contractual interest expense 1,294      
Amortization of debt discount 2,524      
Amortization of debt issuance costs 323      
Interest expense, net $ 4,141      
Effective interest rate of the liability component 5.87%