Face (par) amount of debt instrument at time of issuance.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

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.

+ References

No definition available.

+ Details

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

- Definition

Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28555-108399

+ Details

Name:	us-gaap_DeferredFinanceCostsNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of cash paid for interest, excluding capitalized interest, classified as operating activity. Includes, but is not limited to, payment to settle zero-coupon bond for accreted interest of debt discount and debt instrument with insignificant coupon interest rate in relation to effective interest rate of borrowing attributable to accreted interest of debt discount.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-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

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 17
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3367-108585

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3536-108585

+ Details

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

- Definition

Fair value of the amount outstanding under the credit facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=121572278&loc=d3e13433-108611

+ Details

Name:	us-gaap_LineOfCreditFacilityFairValueOfAmountOutstanding
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Indebtedness divided by net capital.

+ References

No definition available.

+ Details

Name:	us-gaap_RatioOfIndebtednessToNetCapital1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Weighted average interest rate of short-term debt outstanding calculated over time.

+ References

No definition available.

+ Details

Name:	us-gaap_ShortTermDebtWeightedAverageInterestRateOverTime
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

For the form of debt having an initial term of less than one year or less than the normal operating cycle, if longer, average borrowings during the period.

+ References

No definition available.

+ Details

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

- Definition

Number Of Credit Agreements

+ References

No definition available.

+ Details

Name:	wba_NumberOfCreditAgreements
Namespace Prefix:	wba_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Debt - Narrative (Details)	9 Months Ended
Debt - Narrative (Details)	May 31, 2020 USD ($)	May 31, 2019 USD ($)	May 29, 2020 USD ($)	Apr. 15, 2020 USD ($)	Apr. 07, 2020 USD ($)	Apr. 02, 2020 USD ($)	Apr. 01, 2020 USD ($)	Aug. 30, 2019 USD ($) credit_agreement	Jan. 18, 2019 USD ($)	Dec. 21, 2018 USD ($)	Dec. 05, 2018 USD ($)	Aug. 29, 2018 USD ($)
Debt Instrument [Line Items]
Interest paid	$ 510,000,000	$ 570,000,000
Maximum
Debt Instrument [Line Items]
Debt to total capitalization ratio	0.60
Commercial Paper
Debt Instrument [Line Items]
Average daily short-term borrowings	$ 2,600,000,000	$ 2,600,000,000
Weighted average interest rate	2.33%	3.08%
Total $1.5 billion debt issuance
Debt Instrument [Line Items]
Face amount	$ 1,500,000,000			$ 1,500,000,000
Debt issuance costs	$ 13,300,000
Unsecured Notes \| 3.200% unsecured notes due 2030
Debt Instrument [Line Items]
Face amount				$ 500,000,000
Stated interest rate	3.20%			3.20%
Unsecured Notes \| 4.100% unsecured notes due 2050
Debt Instrument [Line Items]
Face amount				$ 1,000,000,000.0
Stated interest rate	4.10%			4.10%
Unsecured Notes \| December 2018 Term Loan Credit Agreement
Debt Instrument [Line Items]
Face amount											$ 1,000,000,000.0
Term Loan \| December 2018 Term Loan Credit Agreement
Debt Instrument [Line Items]
Borrowing outstanding	$ 0
Credit facilities \| April 7, 2020 Revolving Credit Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity					$ 500,000,000
Borrowing outstanding	0
Credit facilities \| April 2020 Revolving Bilateral Credit Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity							$ 750,000,000
Credit facilities \| April 2020 Revolving Club Credit Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity						$ 1,325,000,000
Credit facilities \| Other April 2020 Revolving Credit Agreement
Debt Instrument [Line Items]
Borrowing outstanding	0
Credit facilities \| August 2019 Revolving Credit Agreements
Debt Instrument [Line Items]
Number of credit agreements \| credit_agreement								3
Maximum borrowing capacity								$ 500,000,000
Borrowing outstanding	0
Credit facilities \| January 2019 364-Day Revolving Credit Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity									$ 2,000,000,000.0
Borrowing outstanding	0
Credit facilities \| December 2018 Revolving Credit Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity										$ 1,000,000,000.0
Borrowing outstanding	100,000,000
Credit facilities \| A&R December 2018 Credit Agreement
Debt Instrument [Line Items]
Face amount						2,000,000,000.0
Credit facilities \| August 2018 Revolving Credit Agreement
Debt Instrument [Line Items]
Face amount												$ 3,500,000,000
Borrowing outstanding	0
Credit facilities \| Unsecured Notes \| A&R December 2018 Credit Agreement
Debt Instrument [Line Items]
Face amount						$ 1,000,000,000.0
Credit facilities \| Unsecured Notes \| November 2018 Credit Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity			$ 1,000,000,000.0
Borrowing outstanding	$ 1,000,000,000.0
Credit facilities \| Line of Credit \| November 2018 Credit Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 500,000,000
Letter of Credit \| August 2018 Revolving Credit Agreement
Debt Instrument [Line Items]
Face amount												$ 500,000,000