Fair Value of Financial Instruments - Summary of financial instruments (Details) - USD ($) $ in Thousands	Oct. 03, 2020	Dec. 28, 2019
Financial assets and liabilities measured at fair value on a recurring basis
Total short-term investments	$ 491,428	$ 498,825
Recurring
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	121,718	93,704
Total short-term investments	491,428	498,825
Other assets, net	5,400	5,647
Total assets at fair value	618,546	598,176
Recurring | Money market funds
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	115,033	92,379
Recurring | Corporate debt securities
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	2,350	1,325
Total short-term investments	353,443	326,954
Recurring | Government debt securities
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	4,335
Total short-term investments	137,985	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	119,368	92,379
Total short-term investments	47,252	85,189
Total assets at fair value	166,620	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	115,033	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 cash equivalents	4,335
Total short-term investments	47,252	85,189
Recurring | Significant Other Observable Inputs (Level 2)
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	2,350	1,325
Total short-term investments	444,176	413,636
Total assets at fair value	446,526	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	2,350	1,325
Total short-term investments	353,443	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 short-term investments	90,733	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