Stock Compensation Plans (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	9 Months Ended
May. 31, 2015	May. 31, 2014	May. 31, 2015	May. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock based compensation expense for the period			$ 86	$ 85
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value for options exercised	$ 94		320
Fair value of options vested			52
Cash received from the exercise of options	62		288
Tax benefit from exercise of stock options	$ 35		$ 120
Omnibus Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total shares authorized under Omnibus Plan (in shares)			60,400,000
Omnibus Plan [Member] \| Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options granted in period (in shares)	0	116,478	4,117,968	6,651,240
Total stock based compensation expense for the period	$ 21	$ 33	$ 86	$ 85
Fully recognized retiree eligible expense	$ 0	$ 4	$ 0	$ 12
Grant date fair value (in dollars per share)			$ 14.64
Weighted average volatility rate (in hundredths)			25.51%
Weighted average dividend yield (in hundredths)			1.79%
Expected term			6 years 8 months 5 days
Omnibus Plan [Member] \| Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options granted in period (in shares)	5,823	17,749	1,137,994	658,758
Restricted stock dividend (in shares)	14,097	17,612	51,518	58,070
Total stock based compensation expense for the period	$ 16	$ 17	$ 63	$ 43
Vesting period			3 years
Grant date fair value (in dollars per share)			$ 66.09
Omnibus Plan [Member] \| Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options granted in period (in shares)	0	2,512	484,011	705,451
Vesting period			3 years
Grant date fair value restricted and performance shares (in dollars per share)			$ 65.30

Disclosure of the aggregate tax benefit realized from the exercise of stock options and the conversion of similar instruments during the annual period.

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The cash inflow associated with the amount received from holders exercising their stock options. This item inherently excludes any excess tax benefit, which the entity may have realized and reported separately.

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-Name Accounting Standards Codification

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The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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Weighted average expected volatility rate of share-based compensation awards.

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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.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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Net number of share options (or share units) granted during the period.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The amount of expense recognized during the period for options issued to all employees that are retiree eligible.

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Number of restricted shares of stock issued as dividends during the period.

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Total number of shares available for delivery under the Walgreen Co. Omnibus Incentive Plan

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