Quarterly report pursuant to Section 13 or 15(d)

Debt - Convertible Debt (Details)

v3.10.0.1
Debt - Convertible Debt (Details) - USD ($)
3 Months Ended 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Dec. 31, 2017
May 31, 2017
May 23, 2017
Convertible Debt [Abstract]              
Convertible notes payable, net $ 0   $ 0   $ 281,199,000    
Convertible Senior Notes | Convertible Senior Notes Due November 2022              
Convertible Debt [Abstract]              
Principal amount 345,000,000   345,000,000   345,000,000   $ 345,000,000
Unamortized discount (48,872,000)   (48,872,000)   (56,557,000)    
Unamortized debt issuance costs (6,260,000)   (6,260,000)   (7,244,000)    
Convertible notes payable, net 289,868,000   289,868,000   281,199,000 $ 282,500,000  
Equity component 61,390,000   61,390,000   $ 61,390,000 $ 62,500,000  
Interest Expense, Debt [Abstract]              
Contractual interest expense 1,294,000 $ 1,265,000 3,881,000 $ 1,826,000      
Amortization of debt discount 2,599,000 2,451,000 7,685,000 3,503,000      
Amortization of debt issuance costs 333,000 313,000 984,000 447,000      
Interest expense, net $ 4,226,000 $ 4,029,000 $ 12,550,000 $ 5,776,000