Stockholders' equity - Schedule of Changes in Stockholders' Equity (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2023	Jun. 30, 2022
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning		$ 14,577			$ 14,577
Net income	$ 1,722		$ 2,291		3,430	$ 4,492
Other comprehensive income (loss), net of taxes	6		(27)		8	(23)
Balance, ending	15,940				15,940
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	1,741	1,741	1,741	$ 1,741	1,741	1,741
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	3,016	2,951	2,667	2,630	2,951	2,630
Common stock issued for stock-based awards	36	(37)	31	(36)
Stock compensation	111	104	85	74
Other		(2)		(1)
Balance, ending	3,163	3,016	2,783	2,667	3,163	2,783
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	50,930	50,353	47,053	45,919	50,353	45,919
Net income	1,722	1,708	2,291	2,201
Dividends declared and paid	(1,125)	(1,125)	(1,060)	(1,063)
Dividend equivalents on RSUs	(5)	(6)	(4)	(5)
Other				1
Balance, ending	51,522	50,930	48,280	47,053	51,522	48,280
Treasury Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	(40,192)	(40,214)	(37,291)	(36,800)	(40,214)	(36,800)
Common stock issued for stock-based awards	29	118	25	93
Stock repurchases	(77)	(96)	(1,266)	(584)
Balance, ending	(40,240)	(40,192)	(38,532)	(37,291)	(40,240)	(38,532)
AOCI
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	(252)	(254)	(153)	(157)	(254)	(157)
Other comprehensive income (loss), net of taxes	6	2	(27)	4
Balance, ending	$ (246)	$ (252)	$ (180)	$ (153)	$ (246)	$ (180)