Related Party Transactions - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Common stock, shares issued	34,300,209	34,707,924	34,300,209
Rent expense		$ 4,200,000	$ 4,500,000	$ 4,000,000
Adwest Technologies, Inc. ('Adwest') [Member]
Related Party Transaction [Line Items]
Rent expense paid to former owner		$ 0
Common Stock [Member]
Related Party Transaction [Line Items]
Common stock, shares issued	89,640		89,640
Share purchased		0	105,000	0
Common Stock [Member] | Current Segment President [Member]
Related Party Transaction [Line Items]
Share purchased	75,000		75,000
Adwest, Zhongli, and Emtrol Subsidiaries [Member]
Related Party Transaction [Line Items]
Rent expense		$ 600,000	$ 1,100,000	$ 1,100,000
Zhongli Subsidiary [Member]
Related Party Transaction [Line Items]
Purchase of inventory		800,000	800,000	300,000
Sale of inventory		100,000	0	400,000
Consulting Services [Member] | Related Party One [Member]
Related Party Transaction [Line Items]
Rent and other expenses paid		300,000	400,000	400,000
Consulting Services [Member] | Related Party Two [Member]
Related Party Transaction [Line Items]
Rent and other expenses paid		$ 100,000	$ 100,000	$ 300,000