Quarterly financial data (unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 4,076	$ 3,817	$ 3,239	$ 3,329	$ 3,350	$ 3,771	$ 3,668	$ 3,594	$ 14,461	$ 14,383	$ 15,784
Gross profit	2,646	2,453	2,082	2,088	2,097	2,446	2,360	2,261	9,269	9,164	10,277
Acquisition charges	47	51	50	50	50	79	80	79	198	288	318
Restructuring charges/other	0	0	24	0	0	0	(36)	0	24	(36)	3
Operating profit	1,813	1,609	1,228	1,244	1,249	1,589	1,506	1,379	5,894	5,723	6,713
Net income	$ 1,688	$ 1,353	$ 1,380	$ 1,174	$ 1,070	$ 1,425	$ 1,305	$ 1,217	$ 5,595	$ 5,017	$ 5,580
Basic earnings per common share (in dollars per share)	$ 1.83	$ 1.47	$ 1.50	$ 1.25	$ 1.14	$ 1.51	$ 1.38	$ 1.29	$ 6.05	$ 5.33	$ 5.71
Diluted earnings per common share (in dollars per share)	$ 1.80	$ 1.45	$ 1.48	$ 1.24	$ 1.12	$ 1.49	$ 1.36	$ 1.26	$ 5.97	$ 5.24	$ 5.59