2016 Restructuring - Additional Information (Detail)		3 Months Ended		9 Months Ended
	Jul. 28, 2016 Employee	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017
Restructuring costs and Reserve [Line Items]
Effective date of restructuring				Jul. 28, 2016
Number of employees impacted by workforce reduction | Employee	33
Percentage of pre-reduction headcount impacted by workforce reduction	17.00%
Pre-tax restructuring charges		$ 178,000	$ 807,000
Payments of restructuring charges			619,000
Selling, general and administrative expenses [Member]
Restructuring costs and Reserve [Line Items]
Pre-tax restructuring charges			17,000
Cost of revenue [Member]
Restructuring costs and Reserve [Line Items]
Pre-tax restructuring charges			$ 790,000