Commitments and Contingencies - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) Customer	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Concentration Risk [Line Items]
Number of customers accounted for sale | Customer	10
Rent expense | $	$ 0.2	$ 0.2	$ 0.1
Customer Concentration Risk | Consolidated Sales | Ten Largest Customers
Concentration Risk [Line Items]
Sales Revenue, percentage	44.00%	46.00%	48.00%
Customer Concentration Risk | Consolidated Sales | Customer One | Security Products
Concentration Risk [Line Items]
Sales Revenue, percentage	16.00%	14.00%	13.00%
Customer Concentration Risk | Consolidated Sales | Customer Two | Security Products
Concentration Risk [Line Items]
Sales Revenue, percentage		11.00%	12.00%