Summary of Restructuring Reserve (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Restructuring And Related Activities [Abstract]
Restructuring reserve beginning balance	$ 2,933	$ 1,588
Restructuring expenses incurred during the period		3,020
Amounts paid during the period	(711)	(1,675)
Reversal of cease-use liability	$ (2,222)
Restructuring reserve ending balance		$ 2,933