Stockholders' equity (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	$ 16,273
Net income	1,545	$ 1,179
Other comprehensive income (loss), net of taxes	1	$ (7)
Balance, ending	$ 16,778
Cash dividends declared per common share (in dollars per share)	$ 1.42	$ 1.36
Cash dividends paid per common share (in dollars per share)	$ 1.42	$ 1.36
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	4,511	3,935
Common stock issued for stock-based awards	105	8
Stock compensation	109	116
Other	(3)	(1)
Balance, ending	4,722	4,058
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	52,236	52,262
Net income	1,545	1,179
Dividends declared and paid	(1,291)	(1,238)
Dividend equivalents on RSUs	(8)	(7)
Other	1
Balance, ending	52,483	52,196
Treasury Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	(42,130)	(40,895)
Common stock issued for stock-based awards	204	110
Stock repurchases	(158)	(657)
Balance, ending	(42,084)	(41,442)
AOCI
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning	(85)	(140)
Other comprehensive income (loss), net of taxes	1	(7)
Balance, ending	$ (84)	$ (147)