Annual report pursuant to Section 13 and 15(d)

Concentrations (Details)

v3.8.0.1
Concentrations (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Concentration Risk [Line Items]        
Cash and cash equivalents $ 48,260 $ 50,686 $ 223,552 $ 197,648
Foreign        
Concentration Risk [Line Items]        
Cash and cash equivalents $ 19,700      
Customer Concentration Risk | Sales Revenue        
Concentration Risk [Line Items]        
Concentration risk 19.00% 22.00% 23.00%  
Customer Concentration Risk | Sales Revenue | Connectivity        
Concentration Risk [Line Items]        
Concentration risk 36.00% 54.00% 85.00%  
Customer Concentration Risk | Accounts Receivable | Connectivity        
Concentration Risk [Line Items]        
Concentration risk 10.00% 12.00% 6.00%