Financial Instruments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
Feb. 29, 2012	Feb. 29, 2012	Aug. 31, 2011	Feb. 28, 2011
Fair Value Hedges [Abstract]
Interest rate swaps designated as hedges	$ 1,550	$ 1,550	$ 1,550	$ 1,300
Net unamortized fair value changes in long-term debt	41	41	57	40
Interest Rate Contract [Member] \| Other non-currents assets [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative asset designated as hedging instrument	55	55	63	38
Gain on hedge ineffectiveness	$ 0	$ 0

Fair value of a derivative asset (or nonderivative instrument) that is designated and qualifies as a hedging instrument, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 205G

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 44C

-Subparagraph a

-Clause 1

+ Details

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

- Details

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

- Definition

Gain recognized in earnings during the reporting period representing the amount of the fair value hedges' ineffectiveness.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 45

-Subparagraph a(1)

+ Details

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

- Details

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

- Definition

Aggregate notional amount of all interest rate derivatives designated as hedging instruments in fair value hedges. Notional amount refers to the monetary amount specified in the interest rate derivative contract.

+ References

No definition available.

+ Details

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

- Definition

The net unamortized fair value changes attributable to the hedged risk that are included in long-term debt.

+ References

No definition available.

+ Details

Name:	wag_NetUnamortizedFairValueChangesInLongTermDebt
Namespace Prefix:	wag_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant