Stockholders' equity (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning			$ 16,897				$ 16,897
Net income	$ 1,362			$ 1,709			3,594	$ 5,139
Other comprehensive income (loss), net of taxes	5			$ 11			10	19
Balance, ending	$ 17,268						17,268
Cash dividends declared per common share (in dollars per share)	$ 1.30	$ 1.30	$ 1.30	$ 1.24	$ 1.24	$ 1.24
Cash dividends paid per common share (in dollars per share)	$ 1.30	$ 1.30	$ 1.30	$ 1.24	$ 1.24	$ 1.24
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	3,666	3,439	3,362	3,163	3,016	2,951	3,362	2,951
Common stock issued for stock-based awards	62	111	(29)	38	36	(37)
Stock compensation	87	116	106	79	111	104
Other	(2)		0	0		(2)
Balance, ending	3,813	3,666	3,439	3,280	3,163	3,016	3,813	3,280
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	52,135	52,199	52,283	51,522	50,930	50,353	52,283	50,353
Net income	1,362	1,127	1,105	1,709	1,722	1,708
Dividends declared and paid	(1,187)	(1,185)	(1,183)	(1,126)	(1,125)	(1,125)
Dividend equivalents on RSUs	(6)	(6)	(7)	(6)	(5)	(6)
Other	0		1	(1)		0
Balance, ending	52,304	52,135	52,199	52,098	51,522	50,930	52,304	52,098
Treasury Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	(40,128)	(40,193)	(40,284)	(40,240)	(40,192)	(40,214)	(40,284)	(40,214)
Common stock issued for stock-based awards	55	137	94	35	29	118
Stock repurchases	(322)	(72)	(3)	(48)	(77)	(96)
Balance, ending	(40,395)	(40,128)	(40,193)	(40,253)	(40,240)	(40,192)	(40,395)	(40,253)
AOCI
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	(200)	(203)	(205)	(246)	(252)	(254)	(205)	(254)
Other comprehensive income (loss), net of taxes	5	3	2	11	6	2
Balance, ending	$ (195)	$ (200)	$ (203)	$ (235)	$ (246)	$ (252)	$ (195)	$ (235)