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Investments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
Investments (Details) - USD ($) $ in Millions	Sep. 26, 2020	Sep. 28, 2019	Sep. 26, 2020	Sep. 28, 2019	Dec. 31, 2019
Investments
Fair Value	$ 1,245		$ 1,245		$ 1,434
Total trading short-term investments	1,245		1,245		1,434
Change in unrealized gains (losses) on trading securities	53	$ 2	(45)	$ 124
Domestic equity securities
Investments
Fair Value	613		613		706
Domestic debt securities
Investments
Fair Value	391		391		409
Foreign equity securities
Investments
Fair Value	107		107		189
Foreign equity securities \| Denominated in foreign currencies
Investments
Fair Value Equity	1		1		62
Foreign equity securities \| Denominated in Canadian dollars
Investments
Fair Value Equity	1		1
Foreign equity securities \| Denominated in Euros
Investments
Fair Value Equity					32
Foreign equity securities \| Denominated in Japanese Yen
Investments
Fair Value Equity					12
Foreign equity securities \| Denominated in British pounds
Investments
Fair Value Equity					8
Foreign equity securities \| Denominated in other foreign currencies
Investments
Fair Value Equity					10
Foreign debt securities
Investments
Fair Value	57		57		43
Foreign debt securities \| Denominated in Euros
Investments
Fair Value	21		21		13
High yield securities
Investments
Fair Value	55		55		56
Money market funds held in trading accounts
Investments
Fair Value	2		2		12
Collateralized loan obligations
Investments
Fair Value	16		16		15
Other trading securities
Investments
Fair Value	$ 4		$ 4		$ 4