Fair Value of Financial Instruments - Summary of financial instruments (Details) - USD ($) $ in Thousands	Apr. 04, 2020	Dec. 28, 2019
Financial assets and liabilities measured at fair value on a recurring basis
Total short-term investments	$ 442,493	$ 498,825
Recurring
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	173,483	93,704
Total short-term investments	442,493	498,825
Other assets, net	5,400	5,647
Total assets at fair value	621,376	598,176
Recurring | Money market funds
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	167,636	92,379
Recurring | Corporate debt securities
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	5,847	1,325
Total short-term investments	304,122	326,954
Recurring | Government debt securities
Financial assets and liabilities measured at fair value on a recurring basis
Total short-term investments	138,371	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	167,636	92,379
Total short-term investments	85,519	85,189
Total assets at fair value	253,155	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	167,636	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	85,519	85,189
Recurring | Significant Other Observable Inputs (Level 2)
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	5,847	1,325
Total short-term investments	356,974	413,636
Total assets at fair value	362,821	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	5,847	1,325
Total short-term investments	304,122	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	52,852	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