Summary of Income Tax Benefit (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Apr. 01, 2017
Summary of income tax benefit
Tax provision based on net income	$ 2,571	$ 1,891
Benefit of ASU 2016-09	(2,723)	(3,562)
Total income tax benefit	$ (152)	$ (1,671)