Goodwill and other intangible assets - Goodwill (Detail) - USD ($) $ in Millions		3 Months Ended		12 Months Ended
		Mar. 31, 2022		Dec. 31, 2021
Goodwill And Intangible Assets Disclosure [Abstract]
Balance at beginning of year		$ 73,875	[1]	$ 73,734
Business acquisitions		5		353
Other, including foreign currency translation		(58)		(212)
Balance at end of period	[1]	$ 73,822		$ 73,875

[1] Net of accumulated goodwill impairments of $11.0 billion as of March 31, 2022 and December 31, 2021.