Stockholders' equity - Schedule of Changes in Stockholders' Equity (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning			$ 14,577				$ 14,577
Net income	$ 1,709			$ 2,295			5,139	$ 6,787
Other comprehensive income (loss), net of taxes	11			26			19	3
Balance, ending	16,631						16,631
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	1,741	$ 1,741	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	1,741	1,741
Paid-in Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	3,163	3,016	2,951	2,783	2,667	2,630	2,951	2,630
Common stock issued for stock-based awards	38	36	(37)	26	31	(36)
Stock compensation	79	111	104	68	85	74
Other	0		(2)			(1)
Balance, ending	3,280	3,163	3,016	2,877	2,783	2,667	3,280	2,877
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	51,522	50,930	50,353	48,280	47,053	45,919	50,353	45,919
Net income	1,709	1,722	1,708	2,295	2,291	2,201
Dividends declared and paid	(1,126)	(1,125)	(1,125)	(1,051)	(1,060)	(1,063)
Dividend equivalents on RSUs	(6)	(5)	(6)	(5)	(4)	(5)
Other	(1)					1
Balance, ending	52,098	51,522	50,930	49,519	48,280	47,053	52,098	49,519
Treasury Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	(40,240)	(40,192)	(40,214)	(38,532)	(37,291)	(36,800)	(40,214)	(36,800)
Common stock issued for stock-based awards	35	29	118	52	25	93
Stock repurchases	(48)	(77)	(96)	(996)	(1,266)	(584)
Balance, ending	(40,253)	(40,240)	(40,192)	(39,476)	(38,532)	(37,291)	(40,253)	(39,476)
AOCI
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	(246)	(252)	(254)	(180)	(153)	(157)	(254)	(157)
Other comprehensive income (loss), net of taxes	11	6	2	26	(27)	4
Balance, ending	$ (235)	$ (246)	$ (252)	$ (154)	$ (180)	$ (153)	$ (235)	$ (154)