Goodwill and other intangible assets - Intangible assets - Narrative (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
Intangible asset amortization expense	$ 1,317	$ 1,393	$ 1,469
Estimated amortization expense - 2020	1,275
Estimated amortization expense - 2021	1,144
Estimated amortization expense - 2022	1,082
Estimated amortization expense - 2023	993
Estimated amortization expense - 2024	913
Intangible assets with indefinite lives, excluding goodwill	$ 19,000	$ 18,900