Revenue Recognition - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Standard payment terms to customers			30 days
Losses recognized on fixed-price contracts	$ 0	$ 0	$ 0	$ 0
Maintenance fee revenue recognition period			1 year
Minimum [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Warranty period on fixed-price contracts			30 days
Maximum [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Warranty period on fixed-price contracts			60 days