Income taxes (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
May 31, 2020	May 31, 2019	May 31, 2020	May 31, 2019
Income Tax Disclosure [Abstract]
Effective tax rate	2.30%	13.00%	73.80%	14.70%
Income taxes paid			$ 604	$ 824

The amount of cash paid during the current period to foreign, federal, state, and local authorities as taxes on income, net of any cash received during the current period as refunds for the overpayment of taxes.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=121583591&loc=d3e4297-108586

Name:	us-gaap_IncomeTaxesPaidNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration