Quarterly report pursuant to Section 13 or 15(d)

Debt (Summary) (Details)

v3.10.0.1
Debt (Summary) (Details) - USD ($)
$ in Thousands
Sep. 30, 2018
Dec. 31, 2017
Dec. 15, 2014
Outstanding debt obligations      
Unamortized issuance costs on Convertible Notes $ (2,465) $ (3,106)  
Revolving credit facility balance 0 81,168  
Convertible Notes due 2019      
Outstanding debt obligations      
Face amount 172,500 172,500 $ 172,500
Unaccreted discount on Convertible Notes (7,363) (11,677)  
Unamortized issuance costs on Convertible Notes (1,134) (1,833)  
Convertible Notes carrying value 164,003 158,990  
Convertible Notes due 2023      
Outstanding debt obligations      
Face amount 345,000 0  
Unaccreted discount on Convertible Notes (44,886) 0  
Unamortized issuance costs on Convertible Notes (8,036) 0  
Convertible Notes carrying value 292,078 0  
Credit Agreement      
Outstanding debt obligations      
Revolving credit facility balance $ 0 $ 81,168