Pension and postretirement benefits - Contributions to Employee Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 30, 2024	Apr. 01, 2023	Dec. 30, 2023
Defined Benefit Plan Disclosure [Line Items]
Employer contributions to employee benefit plans	$ 3	$ 0	$ 0
Total current year projected employer contributions	24
Expected future employer contributions, next fiscal year			24
Previously Reported
Defined Benefit Plan Disclosure [Line Items]
Expected future employer contributions, next fiscal year			0
Pension
Defined Benefit Plan Disclosure [Line Items]
Employer contributions to employee benefit plans	3	0	0
Total current year projected employer contributions	24
Nonpension postretirement
Defined Benefit Plan Disclosure [Line Items]
Employer contributions to employee benefit plans	0	$ 0	$ 0
Total current year projected employer contributions	$ 0