Financial Instruments (Narrative) (Details) - USD ($) $ in Millions	Sep. 26, 2020	Dec. 28, 2019
Other Fair Value Disclosure [Line Items]
Short-term investments	$ 475	$ 37
Commercial paper
Other Fair Value Disclosure [Line Items]
Short-term investments	75	37
Commercial paper | Level 2
Other Fair Value Disclosure [Line Items]
Short-term investments	75	37
Mutual Fund | Level 1
Other Fair Value Disclosure [Line Items]
Other assets	$ 42	$ 30