Stockholders' equity (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	$ 16,903
Net income	1,179	$ 1,105
Other comprehensive income (loss), net of taxes	(7)	$ 2
Balance, ending	$ 16,406
Cash dividends declared per common share (in dollars per share)	$ 1.36	$ 1.30
Cash dividends paid per common share (in dollars per share)	$ 1.36	$ 1.30
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	3,935	3,362
Common stock issued for stock-based awards	8	(29)
Stock compensation	116	106
Other	(1)	0
Balance, ending	4,058	3,439
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	52,262	52,283
Net income	1,179	1,105
Dividends declared and paid	(1,238)	(1,183)
Dividend equivalents on RSUs	(7)	(7)
Other	0	1
Balance, ending	52,196	52,199
Treasury Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	(40,895)	(40,284)
Common stock issued for stock-based awards	110	94
Stock repurchases	(657)	(3)
Balance, ending	(41,442)	(40,193)
AOCI
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	(140)	(205)
Other comprehensive income (loss), net of taxes	(7)	2
Balance, ending	$ (147)	$ (203)