Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jul. 01, 2017	Jun. 30, 2018	Jul. 01, 2017	Dec. 31, 2017
Income Tax [Line Items]
Income tax expense (benefit)	$ 242	$ 741	$ (1)	$ 1,133
Unrecognized tax benefits	5,400		5,400		$ 5,300
Expencted reduction in unrecognized tax benefits	$ 3,600		3,600
Maximum
Income Tax [Line Items]
Income tax expense (benefit)			$ (100)