Annual report pursuant to Section 13 and 15(d)

Segments - Schedule of Activities with Major Customers (Detail)

v3.8.0.1
Segments - Schedule of Activities with Major Customers (Detail)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
USD ($)
customer
Dec. 31, 2016
USD ($)
Dec. 31, 2015
Segment Reporting [Abstract]      
Number of major customers | customer 2    
Panasonic | Customer Concentration Risk | Consolidated Revenue      
Revenue, Major Customer      
Percent of consolidated revenue 19.10% 21.60% 21.00%
Panasonic | Customer Concentration Risk | Accounts Receivable      
Revenue, Major Customer      
Accounts receivable $ 10,200 $ 17,126  
Boeing | Customer Concentration Risk | Consolidated Revenue      
Revenue, Major Customer      
Percent of consolidated revenue 16.80% 15.20% 13.00%
Boeing | Customer Concentration Risk | Accounts Receivable      
Revenue, Major Customer      
Accounts receivable $ 12,969 $ 11,737