Pension and postretirement benefits - Components of Plan Benefit Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 28, 2024	Sep. 30, 2023	Sep. 28, 2024	Sep. 30, 2023
Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2	$ 1	$ 6	$ 1
Interest cost	7	3	21	3
Expected return on plan assets	(9)	(3)	(27)	(3)
Amortization of unrecognized prior service cost	1	0	3	0
Recognized (gain) loss, net	3		3
Curtailment (gain) loss, net	3		3
Remeasurement (gain)/loss		0		0
Total postretirement benefit income	7	1	9	1
Nonpension postretirement
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1	3	1
Interest cost	6	4	18	4
Expected return on plan assets	(15)	(10)	(45)	(10)
Amortization of unrecognized prior service cost	(2)	(1)	(6)	(1)
Remeasurement (gain)/loss		0		0
Total postretirement benefit income	$ (10)	$ (6)	$ (30)	$ (6)