Income taxes - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2023	Jan. 01, 2023	Dec. 31, 2023	Jan. 01, 2023	Jan. 02, 2022	Jan. 03, 2021
Tax Credit Carryforward [Line Items]
Effective income tax rate reconciliation, increase (decrease), percent	(3.00%)		3.90%	(8.20%)
Decrease in foreign tax credits	$ 400
Decrease in foreign tax credits, percent	2.60%
Deferred tax assets, tax basis increase of certain assets due to reorganization		$ 300		$ 300	$ 2,300
Effective income tax rate reconciliation, GILTI, amount			$ 100
Increase (decrease) in deferred tax liabilities, global intangible low-taxed income (GILTI)				300	$ 1,700
Tax benefits from loss on capital assets		1.60%			1.60%
Unrecognized tax benefits	$ 2,485	$ 3,716	2,485	3,716	$ 3,210	$ 3,260
Unrecognized tax benefits, interest on income tax expense			99	136	$ 42
Unrecognized tax benefits, interest on income taxes accrued	$ 264	637	$ 264	637
State and Local Jurisdiction
Tax Credit Carryforward [Line Items]
Effective tax rate reconciliation, net increase (decrease) in tax rate, percent			3.40%		3.20%
Deferred tax assets, net					$ 600
Auris Health | Purchased in-process research and development(1)
Tax Credit Carryforward [Line Items]
Impairment of intangible assets, excluding goodwill		$ 900
Effective income tax rate reconciliation, nondeductible expense, impairment losses, percent		22.40%
Talc | Consumer Health
Tax Credit Carryforward [Line Items]
Litigation expense			$ 7,000	$ 1,600
Effective income tax rate reconciliation, tax settlement, percent			21.10%
Effective income tax rate reconciliation, litigation settlement, percent				0.235
Risperdal | Consumer Health
Tax Credit Carryforward [Line Items]
Litigation expense				$ 800
Effective income tax rate reconciliation, litigation settlement, percent				0.164