Cash and Investments (Details) - USD ($) $ in Thousands	Dec. 29, 2018	Dec. 30, 2017
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 151,878	$ 117,162
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(86)	(133)
Estimated Fair Market Value	151,792	117,029
Cash [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	108,845	34,643
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Market Value	108,845	34,643
Money market funds [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	113	256
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Market Value	113	256
Commercial paper [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	1,993
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Estimated Fair Market Value	1,993
Certificates of deposits [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	9,500	14,498
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(3)	(1)
Estimated Fair Market Value	9,497	14,497
U.S. Government agency securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		1,500
Gross Unrealized Gains		0
Gross Unrealized Losses		(5)
Estimated Fair Market Value		1,495
Commercial paper [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	7,933	7,952
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	(3)
Estimated Fair Market Value	7,932	7,949
Corporate debt securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	15,788	48,073
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(58)	(105)
Estimated Fair Market Value	15,730	47,968
Asset-backed Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	7,706	10,240
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(24)	(19)
Estimated Fair Market Value	$ 7,682	$ 10,221

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 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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