Financial Instruments - Investments - Unrealized Gains and Losses Related to Equity Securities (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 27, 2020	Sep. 29, 2019	Sep. 27, 2020	Sep. 29, 2019
Fair Value Disclosures [Abstract]
Net (gains)/losses recognized during the period on equity securities	[1],[2]	$ 70	$ (6)	$ (408)	$ (153)
Less: Net (gains)/losses recognized during the period on equity securities sold during the period		2	(3)	(16)	(13)
Net unrealized (gains)/losses during the reporting period on equity securities still held at the reporting date	[3]	$ 68	$ (3)	$ (391)	$ (140)

[1] The losses in the third quarter of 2020 include, among other things, unrealized losses of $131 million related to our investment in Allogene. The gains in the first nine months of 2020 include, among other things, unrealized gains of $243 million related to our investment in Allogene and unrealized gains of $154 million related to our investment in BioNTech. The gains in the first nine months of 2019 included, among other things, unrealized gains of $115 million related to our investments in Cortexyme, Inc. and SpringWorks Therapeutics, Inc. For additional information on investments, see Note 7B.

[2] Reported in Other (income)/deductions––net. See Note 4.

[3] Included in net unrealized gains are observable price changes on equity securities without readily determinable fair values. Since January 1, 2018, there were cumulative impairments and downward adjustments of $82 million and upward adjustments of $63 million. Impairments, downward and upward adjustments were not significant in the third quarters and the first nine months of 2020 and 2019.