Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements (Narrative) (Details)

v3.19.2
Fair Value Measurements (Narrative) (Details) - USD ($)
Jun. 30, 2019
Dec. 31, 2018
May 25, 2018
Dec. 15, 2014
Fair Value Measurements        
Convertible Notes due 2023 $ 300,078,000 $ 294,725,000    
2019 Convertible Notes        
Fair Value Measurements        
Face amount       $ 172,500,000
Debt instrument, fair value disclosure 193,983,000 174,101,000    
2023 Convertible Notes        
Fair Value Measurements        
Face amount     $ 345,000,000  
Debt instrument, fair value disclosure 411,896,000 339,024,000    
Second Amended and Restated Credit Agreement        
Fair Value Measurements        
Revolving credit facility balance 145,000,000 0    
Carrying Value | 2019 Convertible Notes        
Fair Value Measurements        
Convertible Notes due 2023 169,182,000 165,711,000    
Carrying Value | 2023 Convertible Notes        
Fair Value Measurements        
Convertible Notes due 2023 $ 300,078,000 $ 294,725,000