Restructuring Charges - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Restructuring And Related Activities [Abstract]
Restructuring charges		$ 800,000
Additional restructuring charges	$ 0
Restructuring payments expected to be paid in remainder of 2018	100,000
Restructuring payments expected to be paid in 2018 or beyond	$ 100,000