Fair Value of Financial Instruments - Summary of financial instruments (Details) - USD ($) $ in Thousands	Jul. 04, 2020	Dec. 28, 2019
Financial assets and liabilities measured at fair value on a recurring basis
Total short-term investments	$ 445,685	$ 498,825
Recurring
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	203,980	93,704
Total short-term investments	445,685	498,825
Other assets, net	5,400	5,647
Total assets at fair value	655,065	598,176
Recurring | Money market funds
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	179,239	92,379
Recurring | Corporate debt securities
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	2,397	1,325
Total short-term investments	322,833	326,954
Recurring | Government debt securities
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	22,344
Total short-term investments	122,852	171,871
Recurring | Auction rate securities
Financial assets and liabilities measured at fair value on a recurring basis
Other assets, net	5,400	5,647
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	179,239	92,379
Total short-term investments	77,409	85,189
Total assets at fair value	256,648	177,568
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Money market funds
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	179,239	92,379
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Government debt securities
Financial assets and liabilities measured at fair value on a recurring basis
Total short-term investments	77,409	85,189
Recurring | Significant Other Observable Inputs (Level 2)
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	24,741	1,325
Total short-term investments	368,276	413,636
Total assets at fair value	393,017	414,961
Recurring | Significant Other Observable Inputs (Level 2) | Corporate debt securities
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	2,397	1,325
Total short-term investments	322,833	326,954
Recurring | Significant Other Observable Inputs (Level 2) | Government debt securities
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	22,344
Total short-term investments	45,443	86,682
Recurring | Significant Unobservable Inputs (Level 3)
Financial assets and liabilities measured at fair value on a recurring basis
Other assets, net	5,400	5,647
Total assets at fair value	5,400	5,647
Recurring | Significant Unobservable Inputs (Level 3) | Auction rate securities
Financial assets and liabilities measured at fair value on a recurring basis
Other assets, net	$ 5,400	$ 5,647