Summary of major accounting policies - reconciliation of cash, cash equivalents and restricted cash (Details) - USD ($) $ in Millions	Aug. 31, 2022	Aug. 31, 2021	Aug. 31, 2020	Aug. 31, 2019
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 1,358	$ 559
Marketable securities	1,114	634
Cash, cash equivalents, marketable securities and restricted cash	2,558	1,270	$ 746	$ 1,207
Continuing operations
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	1,358	559
Marketable securities	1,114	634
Restricted cash	$ 86	$ 77

Amount of cash and cash equivalents, and cash and cash equivalents restricted to withdrawal or usage. Excludes amount for disposal group and discontinued operations. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 24
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3521-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 4
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3044-108585

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 8
-URI https://asc.fasb.org/extlink&oid=126999549&loc=SL98516268-108586

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Balance Type:	debit
Period Type:	instant