Restructuring (Details) $ in Millions	3 Months Ended
Nov. 30, 2015 USD ($) Stores	Nov. 30, 2014 USD ($)
Restructuring Reserve Disclosures [Abstract]
Pre-tax charges incurred during the period	$ 90	$ 632
Total restructuring costs	90	17
Retail Pharmacy USA [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	85	17
Retail Pharmacy International [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	5	0
Pharmaceutical Wholesale [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	0	0
Real Estate Costs [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	52	17
Real Estate Costs [Member] \| Retail Pharmacy USA [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	52	17
Real Estate Costs [Member] \| Retail Pharmacy International [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	0	0
Real Estate Costs [Member] \| Pharmaceutical Wholesale [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	0	0
Asset Impairments [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	25	0
Asset Impairments [Member] \| Retail Pharmacy USA [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	25	0
Asset Impairments [Member] \| Retail Pharmacy International [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	0	0
Asset Impairments [Member] \| Pharmaceutical Wholesale [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	0	0
Severance and Other Business Transition and Exit Costs [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	13	0
Severance and Other Business Transition and Exit Costs [Member] \| Retail Pharmacy USA [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	8	0
Severance and Other Business Transition and Exit Costs [Member] \| Retail Pharmacy International [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	5	0
Severance and Other Business Transition and Exit Costs [Member] \| Pharmaceutical Wholesale [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	$ 0	0
Lease Termination Costs [Member]
Restructuring Reserve Disclosures [Abstract]
Pre-tax charges incurred during the period		17
Cost Transformation Program [Member]
Restructuring Reserve Disclosures [Abstract]
Number of stores planned to be closed \| Stores	200
Cost Transformation Program [Member] \| Minimum [Member]
Restructuring Reserve Disclosures [Abstract]
Expected pre-tax charges	$ 1,600
Cost Transformation Program [Member] \| Maximum [Member]
Restructuring Reserve Disclosures [Abstract]
Expected pre-tax charges	1,800
Cost Transformation Program [Member] \| Real Estate Costs [Member]
Restructuring Reserve Disclosures [Abstract]
Pre-tax charges incurred during the period	52	254
Cost Transformation Program [Member] \| Real Estate Costs [Member] \| Minimum [Member]
Restructuring Reserve Disclosures [Abstract]
Expected pre-tax charges	525
Cost Transformation Program [Member] \| Real Estate Costs [Member] \| Maximum [Member]
Restructuring Reserve Disclosures [Abstract]
Expected pre-tax charges	600
Cost Transformation Program [Member] \| Asset Impairments [Member]
Restructuring Reserve Disclosures [Abstract]
Pre-tax charges incurred during the period	25	248
Cost Transformation Program [Member] \| Asset Impairments [Member] \| Minimum [Member]
Restructuring Reserve Disclosures [Abstract]
Expected pre-tax charges	650
Cost Transformation Program [Member] \| Asset Impairments [Member] \| Maximum [Member]
Restructuring Reserve Disclosures [Abstract]
Expected pre-tax charges	725
Cost Transformation Program [Member] \| Severance and Other Business Transition and Exit Costs [Member]
Restructuring Reserve Disclosures [Abstract]
Pre-tax charges incurred during the period	13	$ 130
Cost Transformation Program [Member] \| Severance and Other Business Transition and Exit Costs [Member] \| Minimum [Member]
Restructuring Reserve Disclosures [Abstract]
Expected pre-tax charges	425
Cost Transformation Program [Member] \| Severance and Other Business Transition and Exit Costs [Member] \| Maximum [Member]
Restructuring Reserve Disclosures [Abstract]
Expected pre-tax charges	$ 475

Amount expected to be recognized in earnings for the specified restructuring cost.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 5.P.4(b))
-URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140904-122747

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 5
-Section P
-Subsection 3, 4

+ Details

Name:	us-gaap_RestructuringAndRelatedCostExpectedCost1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Discloses the amount charged against the accrued restructuring reserves, or earnings if not previously accrued, during the period for the specified type of restructuring cost.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB TOPIC 5.P.4(b))
-URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140904-122747

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 5
-Section P
-Subsection 3, 4

+ Details

Name:	us-gaap_RestructuringAndRelatedCostIncurredCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount, after cash payment, of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585

+ Details

Name:	us-gaap_RestructuringCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

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

- Definition

Approximate number of store closed as a part of the restructuring program.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=wba_RetailPharmacyUSAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=wba_RetailPharmacyInternationalMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=wba_PharmaceuticalWholesaleMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RestructuringCostAndReserveAxis=wba_RealEstateCostMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RestructuringCostAndReserveAxis=wba_AssetImpairmentRestructuringChargesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RestructuringCostAndReserveAxis=us-gaap_EmployeeSeveranceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RestructuringCostAndReserveAxis=us-gaap_ContractTerminationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RestructuringPlanAxis=wba_CostTransformationRestructuringProgramMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: