Leases - narrative (Details) - USD ($) $ in Millions	12 Months Ended
Aug. 31, 2020	Aug. 31, 2019
Lessee, Lease, Description [Line Items]
Term of renewal contract	5 years
Charges related to facilities that were closed or relocated	$ 185	$ 129
Minimum
Lessee, Lease, Description [Line Items]
Term of lease	15 years
Maximum
Lessee, Lease, Description [Line Items]
Term of lease	25 years

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

+ Details

Name:	us-gaap_LesseeLeaseDescriptionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Term of lessee's operating lease renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=121609121&loc=SL77918673-209980

+ Details

Name:	us-gaap_LesseeOperatingLeaseRenewalTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Definition

Term of lessee's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

+ Details

Name:	us-gaap_LesseeOperatingLeaseTermOfContract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Definition

Charges related to facilities that were closed or relocated under long-term leases. These charges are reported in selling, general and administrative expenses.

+ References

No definition available.

+ Details

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Namespace Prefix:	wba_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

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- Details

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