Quarterly report pursuant to Section 13 or 15(d)

Debt - Convertible Debt (Details)

v3.19.1
Debt - Convertible Debt (Details) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Dec. 31, 2018
May 31, 2017
May 23, 2017
Convertible Debt [Abstract]          
Convertible notes payable, net $ 0   $ 292,843    
Convertible Senior Notes | Convertible Senior Notes Due November 2022          
Convertible Debt [Abstract]          
Principal amount 345,000   345,000   $ 345,000
Unamortized discount (43,559)   (46,235)    
Unamortized debt issuance costs (5,579)   (5,922)    
Convertible notes payable, net 295,862   292,843 $ 282,500  
Equity component 61,390   $ 61,390 $ 62,500  
Interest Expense, Debt [Abstract]          
Contractual interest expense 1,294 $ 1,294      
Amortization of debt discount 2,676 2,524      
Amortization of debt issuance costs 343 323      
Interest expense, net $ 4,313 $ 4,141