Pensions and other benefit plans - Schedule of Defined Benefit Plans Disclosures (Details) - Retirement plans - USD ($) $ in Millions	Dec. 29, 2024	Dec. 31, 2023	Jan. 01, 2023
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	$ 33,395	$ 33,607	$ 31,496
Fair Value, Measurements, Recurring
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	33,395	33,607
Investments Measured at Net Asset Value	10,277	9,967
Fair Value, Measurements, Recurring \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	7,144	7,776
Fair Value, Measurements, Recurring \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	15,809	15,729
Fair Value, Measurements, Recurring \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	165	135
Fair Value, Measurements, Recurring \| Short-term investment funds
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	511	841
Fair Value, Measurements, Recurring \| Short-term investment funds \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	0	12
Fair Value, Measurements, Recurring \| Short-term investment funds \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	511	829
Fair Value, Measurements, Recurring \| Short-term investment funds \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	0	0
Fair Value, Measurements, Recurring \| Government and agency securities
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	7,885	5,985
Fair Value, Measurements, Recurring \| Government and agency securities \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	0	0
Fair Value, Measurements, Recurring \| Government and agency securities \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	7,885	5,985
Fair Value, Measurements, Recurring \| Government and agency securities \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	0	0
Fair Value, Measurements, Recurring \| Debt instruments
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	2,321	3,899
Fair Value, Measurements, Recurring \| Debt instruments \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	0	0
Fair Value, Measurements, Recurring \| Debt instruments \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	2,321	3,899
Fair Value, Measurements, Recurring \| Debt instruments \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	0	0
Fair Value, Measurements, Recurring \| Equity securities
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	7,144	7,764
Fair Value, Measurements, Recurring \| Equity securities \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	7,144	7,764
Fair Value, Measurements, Recurring \| Equity securities \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	0	0
Fair Value, Measurements, Recurring \| Equity securities \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	0	0
Fair Value, Measurements, Recurring \| Commingled funds
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	11,231	11,682
Investments Measured at Net Asset Value	6,190	6,672
Fair Value, Measurements, Recurring \| Commingled funds \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	0	0
Fair Value, Measurements, Recurring \| Commingled funds \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	5,004	4,967
Fair Value, Measurements, Recurring \| Commingled funds \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	37	43
Fair Value, Measurements, Recurring \| Other assets
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	4,303	3,436
Investments Measured at Net Asset Value	4,087	3,295
Fair Value, Measurements, Recurring \| Other assets \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	0	0
Fair Value, Measurements, Recurring \| Other assets \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	88	49
Fair Value, Measurements, Recurring \| Other assets \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	$ 128	$ 92