Accounts Receivable and Sales Concentrations - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net sales	$ 619,793,000	$ 584,954,000	$ 405,443,000
Bosch [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net sales		$ 59.2	$ 73.0
Net Sales [Member] | Customer Concentration Risk [Member] | Bosch [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of consolidated sales		10.00%	18.00%
Accounts Receivable [Member] | Bosch [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable concentrations in excess	10.00%	10.00%