Difference Between Tax Provision at Statutory Federal Income Tax Rate and Tax Provision (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 29, 2018	Dec. 30, 2017
Reconciliation Of Income Taxes [Line Items]
Income tax (benefit) at the federal statutory rate	$ (756)	$ 1,827
State income taxes, net of federal benefit	5	13
Effect of foreign operations taxed at various rates	(254)	(1,036)
Research tax credits	(1,883)	(2,267)
Change in federal tax rate		9,201
Effect of tax rate changes, permanent differences and adjustments of prior deferrals	4,142	639
Unrecognized tax benefits	(74)	202
Total	(7,176)	1,103
United States
Reconciliation Of Income Taxes [Line Items]
Change in valuation allowance	930	(6,873)
Foreign Tax Authority
Reconciliation Of Income Taxes [Line Items]
Change in valuation allowance	$ (9,286)	$ (603)

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