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
	Mar. 31, 2026	Mar. 31, 2025
Basic EPS:
Net income	$ 1,545	$ 1,179
Income allocated to RSUs	(9)	(6)
Income allocated to common stock	$ 1,536	$ 1,173
Weighted average number of shares outstanding, basic (in shares)	909	910
Basic (in dollars per share)	$ 1.69	$ 1.29
Dilutive effect of stock compensation plans (in shares)	5	6
Diluted EPS:
Net income	$ 1,545	$ 1,179
Income allocated to RSUs	(9)	(6)
Income allocated to common stock for diluted EPS	$ 1,536	$ 1,173
Weighted average number of shares outstanding, diluted (in shares)	914	916
Diluted (in dollars per share)	$ 1.68	$ 1.28