Cash, cash equivalents and short-term investments (Detail) - USD ($) $ in Thousands	Apr. 03, 2020	Jan. 03, 2020
Fair Value Measurements [Line Items]
Amortized Cost	$ 151,495	$ 231,277
Gross Unrealized Gains	548	324
Gross Unrealized Losses	0	0
Estimated Fair Value	152,043	231,601
Cash
Fair Value Measurements [Line Items]
Amortized Cost	100,836	135,225
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	100,836	135,225
Money market securities
Fair Value Measurements [Line Items]
Amortized Cost	4,758	41,211
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	4,758	41,211
Total cash equivalents
Fair Value Measurements [Line Items]
Amortized Cost	4,758	41,211
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	4,758	41,211
Total cash and cash equivalents
Fair Value Measurements [Line Items]
Amortized Cost	105,594	176,436
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	105,594	176,436
U.S. Treasury and agency securities
Fair Value Measurements [Line Items]
Amortized Cost	45,901	54,841
Gross Unrealized Gains	548	324
Gross Unrealized Losses	0	0
Estimated Fair Value	46,449	55,165
Total short-term investments
Fair Value Measurements [Line Items]
Amortized Cost	45,901	54,841
Gross Unrealized Gains	548	324
Gross Unrealized Losses	0	0
Estimated Fair Value	$ 46,449	$ 55,165

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Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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