Cash and Investments - Cash, Cash Equivalents and Available-for-Sale Investments (Details) - USD ($) $ in Thousands	Sep. 28, 2019	Dec. 29, 2018
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 144,059	$ 151,878
Gross Unrealized Gains	52	0
Gross Unrealized Losses	(1)	(86)
Estimated Fair Market Value	144,110	151,792
Cash [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	34,862	108,845
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Market Value	34,862	108,845
Money market funds [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	9,162	113
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Market Value	9,162	113
Commercial paper [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	5,985	1,993
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Market Value	5,985	1,993
Certificates of deposits [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	1,000	0
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Market Value	1,000	0
Certificates of deposits [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	29,003	9,500
Gross Unrealized Gains	4	0
Gross Unrealized Losses	0	(3)
Estimated Fair Market Value	29,007	9,497
Commercial paper [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	16,760	7,933
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	(1)
Estimated Fair Market Value	16,759	7,932
Corporate debt securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	36,894	15,788
Gross Unrealized Gains	33	0
Gross Unrealized Losses	0	(58)
Estimated Fair Market Value	36,927	15,730
Asset-backed Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	10,393	7,706
Gross Unrealized Gains	15	0
Gross Unrealized Losses	0	(24)
Estimated Fair Market Value	$ 10,408	$ 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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