Stockholders' equity - Schedule of Changes in Stockholders' Equity (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	$ 13,333
Net income	2,201	$ 1,753
Other comprehensive income (loss), net of taxes	4	13
Balance, ending	14,017
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	2,630	2,333
Common stock issued for stock-based awards	(36)	(3)
Stock compensation	74	61
Other	(1)
Balance, ending	2,667	2,391
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	45,919	42,051
Net income	2,201	1,753
Dividends declared and paid	(1,063)	(940)
Dividend equivalents on RSUs	(5)	(4)
Other	1
Balance, ending	47,053	42,860
Treasury Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	(36,800)	(36,578)
Common stock issued for stock-based awards	93	199
Stock repurchases	(584)	(100)
Balance, ending	(37,291)	(36,479)
AOCI
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	(157)	(360)
Other comprehensive income (loss), net of taxes	4	13
Balance, ending	$ (153)	$ (347)