Restructuring (Details) $ in Millions	12 Months Ended
Aug. 31, 2015 USD ($) Store	Aug. 31, 2014 USD ($)
Restructuring Reserve Disclosures [Abstract]
Pre-tax charges incurred during the period	$ 542	$ 209
Total restructuring costs	559	209
Retail Pharmacy USA [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	540	209
Retail Pharmacy International [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	19	0
Pharmaceutical Wholesale [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	0	0
Asset Impairments [Member]
Restructuring Reserve Disclosures [Abstract]
Pre-tax charges incurred during the period		71
Total restructuring costs	223	71
Asset Impairments [Member] \| Retail Pharmacy USA [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	216	71
Asset Impairments [Member] \| Retail Pharmacy International [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	7	0
Asset Impairments [Member] \| Pharmaceutical Wholesale [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	0	0
Real Estate Costs [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	219	137
Real Estate Costs [Member] \| Retail Pharmacy USA [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	219	137
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
Severance and Other Business Transition and Exit Costs [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	117	1
Severance and Other Business Transition and Exit Costs [Member] \| Retail Pharmacy USA [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	105	1
Severance and Other Business Transition and Exit Costs [Member] \| Retail Pharmacy International [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	12	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	137
Other Charges [Member]
Restructuring Reserve Disclosures [Abstract]
Pre-tax charges incurred during the period		$ 1
Cost Transformation Program [Member]
Restructuring Reserve Disclosures [Abstract]
Number of stores planned to be closed \| Store	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] \| Asset Impairments [Member]
Restructuring Reserve Disclosures [Abstract]
Pre-tax charges incurred during the period	223
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] \| Real Estate Costs [Member]
Restructuring Reserve Disclosures [Abstract]
Pre-tax charges incurred during the period	202
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] \| Severance and Other Business Transition and Exit Costs [Member]
Restructuring Reserve Disclosures [Abstract]
Pre-tax charges incurred during the period	117
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_AssetImpairmentRestructuringChargesMember
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=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_RestructuringCostAndReserveAxis=us-gaap_OtherRestructuringMember
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: