XML 34 R24.htm IDEA: XBRL DOCUMENT v3.8.0.1
Summary of significant accounting policies - Additional Information (Details)
$ in Thousands
3 Months Ended
Mar. 31, 2018
USD ($)
segment
Mar. 31, 2017
USD ($)
Jan. 01, 2018
USD ($)
Dec. 31, 2017
USD ($)
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]        
Number of reportable segments | segment 1      
Number of operating segments | segment 1      
Retained earnings $ (526,336) $ (558,286)   $ (526,972)
Net sales 65,920 60,574    
Accounts receivable $ 31,779 $ 29,135   $ 44,634
Minimum        
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]        
Payment terms 30 days      
Maximum        
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]        
Payment terms 60 days      
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606        
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]        
Retained earnings     $ (100)  
Net sales $ (600)      
Accounts receivable $ (600)