Supplemental Financial Information - Accumulated other comprehensive income (loss) (Details) $ in Millions	9 Months Ended
	Sep. 29, 2019 USD ($)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	$ 10,690
Other comprehensive income (loss) before reclassifications	(67)
Amounts reclassified out of accumulated other comprehensive income (loss)	9
Tax effects	2
Other comprehensive income (loss)	(56)
Balance	9,595
Currency translation differences
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	218
Other comprehensive income (loss) before reclassifications	(47)
Amounts reclassified out of accumulated other comprehensive income (loss)	0
Tax effects	0
Other comprehensive income (loss)	(47)
Balance	171
Change in fair value cash flow hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	(3)
Other comprehensive income (loss) before reclassifications	(14)
Amounts reclassified out of accumulated other comprehensive income (loss)	9
Tax effects	1
Other comprehensive income (loss)	(4)
Balance	(7)
Net actuarial gain/(losses)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	(92)
Other comprehensive income (loss) before reclassifications	(6)
Amounts reclassified out of accumulated other comprehensive income (loss)	0
Tax effects	1
Other comprehensive income (loss)	(5)
Balance	(97)
Accumulated other comprehensive income (loss)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	123
Balance	$ 67