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, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Basic EPS:
Net income	$ 1,709	$ 2,295	$ 5,139	$ 6,787
Income allocated to RSUs	(9)	(11)	(27)	(30)
Income allocated to common stock	$ 1,700	$ 2,284	$ 5,112	$ 6,757
Weighted average number of shares outstanding, basic (in shares)	908	913	908	919
Basic (in dollars per share)	$ 1.87	$ 2.50	$ 5.63	$ 7.35
Dilutive effect of stock compensation plans (in shares)	8	10	8	10
Diluted EPS:
Net income	$ 1,709	$ 2,295	$ 5,139	$ 6,787
Income allocated to RSUs	(10)	(11)	(26)	(30)
Income allocated to common stock for diluted EPS	$ 1,699	$ 2,284	$ 5,113	$ 6,757
Weighted average number of shares outstanding, diluted (in shares)	916	923	916	929
Diluted (in dollars per share)	$ 1.85	$ 2.47	$ 5.58	$ 7.27