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		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Basic EPS:
Net income	$ 2,291	$ 1,931	$ 4,492	$ 3,684
Income allocated to RSUs	(10)	(7)	(19)	(15)
Income allocated to common stock	$ 2,281	$ 1,924	$ 4,473	$ 3,669
Weighted average number of shares outstanding, basic (in shares)	920	923	922	923
Basic (in dollars per share)	$ 2.48	$ 2.08	$ 4.85	$ 3.98
Dilutive effect of stock compensation plans (in shares)	10	14	10	13
Diluted EPS:
Net income	$ 2,291	$ 1,931	$ 4,492	$ 3,684
Income allocated to RSUs	(10)	(7)	(19)	(15)
Income allocated to common stock for diluted EPS	$ 2,281	$ 1,924	$ 4,473	$ 3,669
Weighted average number of shares outstanding, diluted (in shares)	930	937	932	936
Diluted (in dollars per share)	$ 2.45	$ 2.05	$ 4.80	$ 3.92