Related party disclosures - Superannuation plans (Details) - AUD ($) $ in Millions	12 Months Ended
Sep. 30, 2020	Sep. 30, 2019
Related party disclosures
Group contributions to defined contribution plans	$ 361	$ 347
Group contributions to defined benefit plans	$ 26	$ 28

The decrease (increase) in net defined benefit liability (asset) resulting from contributions to a defined benefit plan by the employer. [Refer: Net defined benefit liability (asset); Defined benefit plans [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2019-01-01
-Paragraph 141
-Subparagraph f
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2019-en-r&anchor=para_141_f&doctype=Standard
-URIDate 2019-03-27

Name:	ifrs-full_ContributionsToPlanByEmployerNetDefinedBenefitLiabilityAsset
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration