Cash and Investments (Details) - USD ($) $ in Thousands	Mar. 30, 2019	Dec. 29, 2018
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 148,061	$ 151,878
Gross Unrealized Gains	15	0
Gross Unrealized Losses	(13)	(86)
Estimated Fair Market Value	148,063	151,792
Cash [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	79,697	108,845
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Market Value	79,697	108,845
Money market funds [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	10,526	113
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Market Value	10,526	113
Commercial paper [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	3,989	1,993
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Market Value	3,989	1,993
Certificates of deposits [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	1,000
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Estimated Fair Market Value	1,000
Certificates of deposits [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	11,251	9,500
Gross Unrealized Gains	6	0
Gross Unrealized Losses	0	(3)
Estimated Fair Market Value	11,257	9,497
Commercial paper [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	16,896	7,933
Gross Unrealized Gains	9	0
Gross Unrealized Losses	0	(1)
Estimated Fair Market Value	16,905	7,932
Corporate debt securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	16,269	15,788
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(13)	(58)
Estimated Fair Market Value	16,256	15,730
Asset-backed Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	8,433	7,706
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	(24)
Estimated Fair Market Value	$ 8,433	$ 7,682

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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Amount of 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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