Supplemental Financial Information - Accumulated other comprehensive income (loss) (Details) $ in Millions	3 Months Ended
	Mar. 29, 2020 USD ($)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	$ 9,655
Other comprehensive income (loss) before reclassifications	(58)
Amounts reclassified out of accumulated other comprehensive income (loss)	3
Other comprehensive income (loss)	(6)
Other comprehensive income (loss)	(61)
Balance	9,258
Currency translation differences
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	203
Other comprehensive income (loss) before reclassifications	(49)
Amounts reclassified out of accumulated other comprehensive income (loss)	0
Other comprehensive income (loss)	0
Other comprehensive income (loss)	(49)
Balance	154
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	(16)
Amounts reclassified out of accumulated other comprehensive income (loss)	3
Other comprehensive income (loss)	3
Other comprehensive income (loss)	(10)
Balance	(8)
Net actuarial gain/(losses)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	(130)
Other comprehensive income (loss) before reclassifications	7
Amounts reclassified out of accumulated other comprehensive income (loss)	0
Other comprehensive income (loss)	(9)
Other comprehensive income (loss)	(2)
Balance	(132)
Accumulated other comprehensive income (loss)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	75
Balance	$ 14