Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements (Details)

v3.8.0.1
Fair Value Measurements (Details) - USD ($)
$ in Thousands
Mar. 31, 2018
Dec. 31, 2017
Dec. 15, 2014
Fair Value Measurements      
Convertible Debt, Noncurrent $ 160,638 $ 158,990  
Level 1 | Recurring Basis      
Assets      
Total Assets 14,553 39,400  
Liabilities      
Total liabilities 5,484 4,364  
Level 1 | Recurring Basis | Deferred compensation liability      
Liabilities      
Total liabilities 5,484 4,364  
Level 1 | Recurring Basis | Money market funds      
Assets      
Total Assets 14,553 39,400  
Level 3 | Recurring Basis      
Assets      
Total Assets 5,207 5,185  
Liabilities      
Total liabilities 2,863 2,781  
Level 3 | Recurring Basis | Contingent consideration      
Liabilities      
Total liabilities 2,863 2,781  
Level 3 | Recurring Basis | Asset to fund deferred compensation liability      
Assets      
Total Assets 5,207 5,185  
Fair Value | Recurring Basis      
Assets      
Total Assets 19,760 44,585  
Liabilities      
Total liabilities 8,347 7,145  
Fair Value | Recurring Basis | Contingent consideration      
Liabilities      
Total liabilities 2,863 2,781  
Fair Value | Recurring Basis | Deferred compensation liability      
Liabilities      
Total liabilities 5,484 4,364  
Fair Value | Recurring Basis | Money market funds      
Assets      
Total Assets 14,553 39,400  
Fair Value | Recurring Basis | Asset to fund deferred compensation liability      
Assets      
Total Assets 5,207 5,185  
Convertible Notes      
Fair Value Measurements      
Face amount 172,500 172,500 $ 172,500
Convertible Debt, Noncurrent 160,638 158,990  
Liabilities      
Total liabilities 190,337 180,180  
Convertible Notes | Carrying Value      
Fair Value Measurements      
Convertible Debt, Noncurrent 160,638 158,990  
Revolving credit facility      
Liabilities      
Total liabilities $ 261,168 $ 81,168