Supplemental Financial Information - Accumulated other comprehensive income (loss) (Details) $ in Millions	6 Months Ended
	Jun. 28, 2020 USD ($)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	$ 9,655
Other comprehensive income (loss) before reclassifications	(24)
Amounts reclassified out of accumulated other comprehensive income (loss)	8
Other comprehensive income (loss)	(9)
Other comprehensive income (loss)	(25)
Balance	9,055
Currency  translation differences
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	203
Other comprehensive income (loss) before reclassifications	(23)
Amounts reclassified out of accumulated other comprehensive income (loss)	0
Other comprehensive income (loss)	0
Other comprehensive income (loss)	(23)
Balance	180
Change in fair  value cash flow hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	2
Other comprehensive income (loss) before reclassifications	(7)
Amounts reclassified out of accumulated other comprehensive income (loss)	8
Other comprehensive income (loss)	0
Other comprehensive income (loss)	1
Balance	3
Net actuarial gain/(losses)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	(130)
Other comprehensive income (loss) before reclassifications	6
Amounts reclassified out of accumulated other comprehensive income (loss)	0
Other comprehensive income (loss)	(9)
Other comprehensive income (loss)	(3)
Balance	(133)
Accumulated other comprehensive income (loss)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	75
Balance	$ 50