Inventories - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Inventory Net Items Net Of Reserve Alternative [Abstract]
Inventory reserve balance	$ 300,000		$ 300,000		$ 0
Charges for excess and obsolete inventory	$ 300,000	$ 0	$ 500,000	$ 0