Pensions and other benefit plans - Schedule of Defined Benefit Plans Disclosures (Details) - Retirement plans - USD ($) $ in Millions	Dec. 28, 2025	Dec. 29, 2024	Dec. 31, 2023
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	$ 36,658	$ 33,395	$ 33,607
Fair Value, Measurements, Recurring
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	36,658	33,395
Investments Measured at Net Asset Value	11,037	10,277
Fair Value, Measurements, Recurring \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	6,704	7,144
Fair Value, Measurements, Recurring \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	18,808	15,809
Fair Value, Measurements, Recurring \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	109	165
Fair Value, Measurements, Recurring \| Short-term investment funds
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	734	511
Fair Value, Measurements, Recurring \| Short-term investment funds \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	57	0
Fair Value, Measurements, Recurring \| Short-term investment funds \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	677	511
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	9,149	7,885
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	9,149	7,885
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	2,310	2,321
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	2,310	2,321
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	6,648	7,144
Fair Value, Measurements, Recurring \| Equity securities \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	6,647	7,144
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	1	0
Fair Value, Measurements, Recurring \| Commingled funds
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	12,210	11,231
Investments Measured at Net Asset Value	6,105	6,190
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	6,105	5,004
Fair Value, Measurements, Recurring \| Commingled funds \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	0	37
Fair Value, Measurements, Recurring \| Other assets
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	5,607	4,303
Investments Measured at Net Asset Value	4,932	4,087
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	567	88
Fair Value, Measurements, Recurring \| Other assets \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	$ 108	$ 128