Subsequent Event - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Subsequent Event [Line Items]
Restructuring charge		$ 667	$ 8,118	$ 0
Scenario, Forecast [Member] | Minimum [Member]
Subsequent Event [Line Items]
Restructuring charge	$ 2,300
Scenario, Forecast [Member] | Maximum [Member]
Subsequent Event [Line Items]
Restructuring charge	$ 2,900