Pensions and other benefit plans - Schedule of Defined Benefit Plans Disclosures (Details) - Retirement plans - USD ($) $ in Millions	Dec. 31, 2023	Jan. 01, 2023	Jan. 02, 2022
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	$ 33,607	$ 31,496	$ 41,909
Fair Value, Measurements, Recurring
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	33,607	31,496
Investments Measured at Net Asset Value	9,967	8,602
Fair Value, Measurements, Recurring | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	7,776	8,872
Fair Value, Measurements, Recurring | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	15,729	13,954
Fair Value, Measurements, Recurring | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	135	68
Fair Value, Measurements, Recurring | Short-term investment funds
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	841	39
Fair Value, Measurements, Recurring | Short-term investment funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	12	26
Fair Value, Measurements, Recurring | Short-term investment funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	829	13
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	5,985	5,863
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	5,985	5,863
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	3,899	3,681
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	3,899	3,681
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	7,764	8,848
Fair Value, Measurements, Recurring | Equity securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	7,764	8,846
Fair Value, Measurements, Recurring | Equity securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	0	2
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	11,682	10,514
Investments Measured at Net Asset Value	6,672	6,096
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	4,967	4,362
Fair Value, Measurements, Recurring | Commingled funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	43	56
Fair Value, Measurements, Recurring | Other assets
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	3,436	2,551
Investments Measured at Net Asset Value	3,295	2,506
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	49	33
Fair Value, Measurements, Recurring | Other assets | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan Assets	$ 92	$ 12