Pensions and other benefit plans - Information Related to the Benefit Obligation and the Fair Value of Plan Assets (Details) - USD ($) $ in Millions	Dec. 31, 2023	Jan. 01, 2023
Qualified Plans | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	$ 22,298	$ 20,937
Projected Benefit Obligation	19,152	18,394
Accumulated Benefit Obligation	18,557	17,696
Projected Benefit Obligation	3,146	2,543
Accumulated Benefit Obligation	3,741	3,241
Non-Qualified Plans | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	0	0
Projected Benefit Obligation	2,037	1,937
Accumulated Benefit Obligation	1,982	1,872
Projected Benefit Obligation	(2,037)	(1,937)
Accumulated Benefit Obligation	(1,982)	(1,872)
Funded Plans | International Plans
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	11,309	10,559
Projected Benefit Obligation	10,431	8,982
Accumulated Benefit Obligation	9,498	8,166
Projected Benefit Obligation	878	1,577
Accumulated Benefit Obligation	1,811	2,393
Unfunded Plans | International Plans
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	0	0
Projected Benefit Obligation	124	77
Accumulated Benefit Obligation	102	63
Projected Benefit Obligation	(124)	(77)
Accumulated Benefit Obligation	$ (102)	$ (63)