Basis of presentation and significant accounting policies and practices - Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Basic EPS:
Net income	$ 1,364	$ 1,362	$ 3,838	$ 3,594
Income allocated to RSUs	(8)	(7)	(21)	(18)
Income allocated to common stock	$ 1,356	$ 1,355	$ 3,817	$ 3,576
Weighted average number of shares outstanding, basic (in shares)	909	913	909	912
Basic (in dollars per share)	$ 1.49	$ 1.48	$ 4.20	$ 3.92
Dilutive effect of stock compensation plans (in shares)	5	7	5	7
Diluted EPS:
Net income	$ 1,364	$ 1,362	$ 3,838	$ 3,594
Income allocated to RSUs	(8)	(7)	(21)	(18)
Income allocated to common stock for diluted EPS	$ 1,356	$ 1,355	$ 3,817	$ 3,576
Weighted average number of shares outstanding, diluted (in shares)	914	920	914	919
Diluted (in dollars per share)	$ 1.48	$ 1.47	$ 4.18	$ 3.89