Stockholders' equity - Schedule of Changes in Stockholders' Equity (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2022	Jun. 30, 2021
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning		$ 13,333			$ 13,333
Net income	$ 2,291		$ 1,931		4,492	$ 3,684
Other comprehensive income (loss), net of taxes	(27)		24		(23)	37
Balance, ending	14,092				14,092
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	1,741	1,741	1,741	$ 1,741	1,741	1,741
Other			0
Balance, ending	1,741	1,741	1,741	1,741	1,741	1,741
Paid-in Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	2,667	2,630	2,391	2,333	2,630	2,333
Common stock issued for stock-based awards	31	(36)	25	(3)
Stock compensation	85	74	69	61
Other		(1)	0
Balance, ending	2,783	2,667	2,485	2,391	2,783	2,485
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	47,053	45,919	42,860	42,051	45,919	42,051
Net income	2,291	2,201	1,931	1,753
Dividends declared and paid	(1,060)	(1,063)	(942)	(940)
Dividend equivalents on RSUs	(4)	(5)	(4)	(4)
Other		1	1
Balance, ending	48,280	47,053	43,846	42,860	48,280	43,846
Treasury Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	(37,291)	(36,800)	(36,479)	(36,578)	(36,800)	(36,578)
Common stock issued for stock-based awards	25	93	29	199
Stock repurchases	(1,266)	(584)	(146)	(100)
Other			0
Balance, ending	(38,532)	(37,291)	(36,596)	(36,479)	(38,532)	(36,596)
AOCI
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	(153)	(157)	(347)	(360)	(157)	(360)
Other comprehensive income (loss), net of taxes	(27)	4	24	13
Other			0
Balance, ending	$ (180)	$ (153)	$ (323)	$ (347)	$ (180)	$ (323)