Annual report pursuant to Section 13 and 15(d)

Fair Value Measurements (Details)

v3.8.0.1
Fair Value Measurements (Details) - USD ($)
$ in Thousands
Dec. 31, 2017
Dec. 31, 2016
Dec. 15, 2014
Fair Value Measurements      
Convertible Debt, Noncurrent $ 158,990 $ 152,575  
Term Notes   100,409  
Other non-current assets      
Assets      
Total Assets 5,185    
Level 1 | Recurring Basis      
Assets      
Total Assets 39,400 31,644  
Liabilities      
Total liabilities 4,364 2,885  
Level 1 | Recurring Basis | Deferred compensation liability      
Liabilities      
Total liabilities 4,364 2,885  
Level 1 | Recurring Basis | Money market funds      
Assets      
Total Assets 39,400 31,644  
Level 3 | Recurring Basis      
Assets      
Total Assets 5,185 2,738  
Liabilities      
Total liabilities 2,781 4,868  
Level 3 | Recurring Basis | Contingent consideration      
Liabilities      
Total liabilities 2,781 4,868  
Level 3 | Recurring Basis | Asset to fund deferred compensation liability      
Assets      
Total Assets 5,185 2,738  
Fair Value | Recurring Basis      
Assets      
Total Assets 44,585 34,382  
Liabilities      
Total liabilities 7,145 7,753  
Fair Value | Recurring Basis | Contingent consideration      
Liabilities      
Total liabilities 2,781 4,868  
Fair Value | Recurring Basis | Deferred compensation liability      
Liabilities      
Total liabilities 4,364 2,885  
Fair Value | Recurring Basis | Money market funds      
Assets      
Total Assets 39,400 31,644  
Fair Value | Recurring Basis | Asset to fund deferred compensation liability      
Assets      
Total Assets 5,185 2,738  
Convertible Notes      
Fair Value Measurements      
Face amount 172,500 172,500 $ 172,500
Convertible Debt, Noncurrent 158,990 152,575  
Liabilities      
Total liabilities 180,180 164,824  
Convertible Notes | Carrying Value      
Fair Value Measurements      
Convertible Debt, Noncurrent 158,990 152,575  
Term Notes      
Fair Value Measurements      
Face amount   142,000  
Term Notes   138,335  
Revolving credit facility      
Liabilities      
Total liabilities $ 81,168 $ 0