Quarterly report pursuant to Section 13 or 15(d)

Debt (Summary) (Details)

v3.8.0.1
Debt (Summary) (Details) - USD ($)
$ in Thousands
Mar. 31, 2018
Dec. 31, 2017
Dec. 15, 2014
Outstanding debt obligations      
Unamortized issuance costs on Convertible Notes $ (2,892) $ (3,106)  
Convertible Notes carrying value 160,638 158,990  
Revolving credit facility balance 261,168 81,168  
Convertible Notes      
Outstanding debt obligations      
Face amount 172,500 172,500 $ 172,500
Unaccreted discount on Convertible Notes (10,259) (11,677)  
Unamortized issuance costs on Convertible Notes (1,603) (1,833)  
Convertible Notes carrying value 160,638 158,990  
Credit Agreement      
Outstanding debt obligations      
Revolving credit facility balance $ 261,168 $ 81,168