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, 2023	Mar. 31, 2022
Basic EPS:
Net income	$ 1,708	$ 2,201
Income allocated to RSUs	(9)	(9)
Income allocated to common stock	$ 1,699	$ 2,192
Weighted average number of shares outstanding, basic (in shares)	907	923
Basic (in dollars per share)	$ 1.87	$ 2.37
Dilutive effect of stock compensation plans (in shares)	9	11
Diluted EPS:
Net income	$ 1,708	$ 2,201
Income allocated to RSUs	(9)	(9)
Income allocated to common stock for diluted EPS	$ 1,699	$ 2,192
Weighted average number of shares outstanding, diluted (in shares)	916	934
Diluted (in dollars per share)	$ 1.85	$ 2.35