Goodwill and other intangible assets - Intangible assets - Narrative (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Goodwill [Line Items]
Intangible asset amortization expense		$ 647	$ 658
Intangible assets with indefinite lives, excluding goodwill	$ 18,300	18,300		$ 19,000
Pre tax goodwill impairment	10,000	9,996
Pre tax intangible assets impairment charges	638
PCC [Member]
Goodwill [Line Items]
Pre tax impairment charges	10,000
Goodwill and indefinite-lived intangible assets	$ 31,000	$ 31,000