Stockholders' equity - Schedule of Changes in Stockholders' Equity (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	$ 14,577
Net income	1,708	$ 2,201
Other comprehensive income (loss), net of taxes	2	4
Balance, ending	15,243
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	1,741	1,741
Balance, ending	1,741	1,741
Paid-in Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	2,951	2,630
Common stock issued for stock-based awards	(37)	(36)
Stock compensation	104	74
Other	(2)	(1)
Balance, ending	3,016	2,667
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	50,353	45,919
Net income	1,708	2,201
Dividends declared and paid	(1,125)	(1,063)
Dividend equivalents on RSUs	(6)	(5)
Other		1
Balance, ending	50,930	47,053
Treasury Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	(40,214)	(36,800)
Common stock issued for stock-based awards	118	93
Stock repurchases	(96)	(584)
Balance, ending	(40,192)	(37,291)
AOCI
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	(254)	(157)
Other comprehensive income (loss), net of taxes	2	4
Balance, ending	$ (252)	$ (153)