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, 2024	Mar. 31, 2023
Basic EPS:
Net income	$ 1,105	$ 1,708
Income allocated to RSUs	(5)	(9)
Income allocated to common stock	$ 1,100	$ 1,699
Weighted average number of shares outstanding, basic (in shares)	910	907
Basic (in dollars per share)	$ 1.21	$ 1.87
Dilutive effect of stock compensation plans (in shares)	7	9
Diluted EPS:
Net income	$ 1,105	$ 1,708
Income allocated to RSUs	(5)	(9)
Income allocated to common stock for diluted EPS	$ 1,100	$ 1,699
Weighted average number of shares outstanding, diluted (in shares)	917	916
Diluted (in dollars per share)	$ 1.20	$ 1.85