Earnings per share - Reconciliation of Basic Net Earnings per Share to Diluted Net Earnings per Share (Details) - $ / shares shares in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2023	Oct. 01, 2023	Jul. 02, 2023	Apr. 02, 2023	Jan. 01, 2023	Oct. 02, 2022	Jul. 03, 2022	Apr. 03, 2022	Dec. 31, 2023	Jan. 01, 2023	Jan. 02, 2022
Reconciliation of basic net earnings per share to diluted net earnings per share
Basic net earnings per share from continuing operations (in dollars per share)	$ 1.71	$ 1.71	$ 2.07	$ (0.19)	$ 1.24	$ 1.64	$ 1.62	$ 1.74	$ 5.26	$ 6.23	$ 6.76
Basic net earnings per share from discontinued operations (in dollars per share)	(0.03)	8.61	(0.09)	0.16	0.11	0.06	0.21	0.22	8.62	0.60	1.17
Basic net earnings per share (in dollars per share)	1.68	10.32	1.98	(0.03)	1.35	1.70	1.83	1.96	$ 13.88	$ 6.83	$ 7.93
Average shares outstanding — basic (in shares)									2,533.5	2,625.2	2,632.1
Potential shares exercisable under stock option plans (in shares)									94.1	140.1	138.0
Less: shares repurchased under treasury stock method (in shares)									(67.2)	(101.4)	(96.1)
Average shares outstanding - diluted (in shares)									2,560.4	2,663.9	2,674.0
Diluted net earnings per share from continuing operations (in dollars per share)	1.70	1.69	2.05	(0.19)	1.22	1.62	1.60	1.71	$ 5.20	$ 6.14	$ 6.66
Diluted net earnings per share from discontinuing operations (in dollars per share)	(0.03)	8.52	(0.09)	0.16	0.11	0.06	0.20	0.22	8.52	0.59	1.15
Diluted net earnings per share (in dollars per share)	$ 1.67	$ 10.21	$ 1.96	$ (0.03)	$ 1.33	$ 1.68	$ 1.80	$ 1.93	$ 13.72	$ 6.73	$ 7.81