Annual report pursuant to Section 13 and 15(d)

Industry, Segment and Geographic Information - Concentration (Details)

v3.6.0.2
Industry, Segment and Geographic Information - Concentration (Details) - customer
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Top five customers      
Significant Customers and Vendors      
Number of customers 5 5 5
Net sales | Customer concentration risk      
Significant Customers and Vendors      
Number of customers 2    
Percentage of concentration risk 10.00%    
Net sales | SHI | Customer concentration risk      
Significant Customers and Vendors      
Percentage of concentration risk 19.60% 19.00% 17.40%
Net sales | CDW | Customer concentration risk      
Significant Customers and Vendors      
Percentage of concentration risk 17.90% 17.90% 16.40%
Net sales | Insight Enterprises, Inc. ("Insight") | Customer concentration risk      
Significant Customers and Vendors      
Percentage of concentration risk     11.00%
Net sales | Top five customers      
Significant Customers and Vendors      
Percentage of concentration risk 48.00% 52.00% 52.00%
Net accounts receivable | SHI | Customer concentration risk      
Significant Customers and Vendors      
Percentage of concentration risk 13.30%    
Net accounts receivable | CDW | Customer concentration risk      
Significant Customers and Vendors      
Percentage of concentration risk 23.20%    
Purchases | Vendor concentration risk | Solarwinds      
Significant Customers and Vendors      
Percentage of concentration risk 10.80%    
Purchases | Vendor concentration risk | Sophos      
Significant Customers and Vendors      
Percentage of concentration risk 23.10% 24.20% 14.70%