Income Taxes (Details) - USD ($) $ in Millions		12 Months Ended
		Aug. 31, 2015	Aug. 31, 2014	Aug. 31, 2013
Schedule of Income before Income Tax, Domestic and Foreign [Abstract]
U.S.		$ 2,725	$ 3,386	$ 3,469
Non - U.S.		2,586	171	578
Earnings Before Income Tax Provision		5,311	3,557	4,047
Current provision [Abstract]
Federal		846	1,207	1,122
State		121	109	134
Non - U.S.		128	35	15
Total current provisions for income taxes		1,095	1,351	1,271
Deferred provision [Abstract]
Federal		(23)	183	228
State		(16)	(3)	(2)
Non - U.S.		0	(5)	2
Total deferred provision for income taxes		(39)	175	228
Income tax provision		$ 1,056	$ 1,526	$ 1,499
Difference Between the Statutory Federal Income Tax Rate and the Effective Tax Rate [Abstract]
Federal statutory rate		35.00%	35.00%	35.00%
State income taxes, net of federal benefit		1.30%	1.90%	2.20%
Loss on Alliance Boots call option	[1]	0.00%	8.50%	0.00%
Deferred tax asset recognition	[1]	(4.10%)	0.00%	0.00%
Gain on previously held equity interest		(5.80%)	0.00%	0.00%
Foreign income taxed at non-U.S. rates		(6.20%)	(3.10%)	(0.30%)
Non-taxable income		(2.60%)	0.00%	0.00%
Non-deductible expenses		2.30%	0.30%	1.00%
Other		0.00%	0.30%	(0.90%)
Effective income tax rate		19.90%	42.90%	37.00%
Remaining ownership subject to call option			55.00%
Nondeductible loss on exercise of call option		$ 0	$ 866	$ 0
Deferred tax assets [Abstract]
Postretirement benefits		130	247
Compensation and benefits		224	166
Insurance		68	98
Accrued rent		167	166
Outside basis difference		73	0
Bad debts		67	65
Tax attributes		341	430
Stock compensation		119	131
Other		93	75
Subtotal deferred tax assets		1,282	1,378
Less: Valuation allowance		125	223
Total deferred tax assets		1,157	1,155
Deferred tax liabilities [Abstract]
Accelerated depreciation		1,234	1,244
Inventory		420	407
Intangible assets		1,822	64
Equity method investment		333	387
Deferred income		889	208
Total deferred tax liabilities		4,698	2,310
Net deferred tax liabilities		3,541	1,155
Operating Loss Carryforwards [Line Items]
Income taxes paid		1,300	1,200	1,200
Deferred tax assets operating loss carryforwards subject to expiration		218
Deferred tax assets operating loss carryforwards not subject to expiration		123
Unrecognized tax benefit reported in current income tax liabilities		73
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of year		193	208	197
Gross increases related to business combination		84	0	0
Gross increases related to tax positions in a prior period		45	55	18
Gross decreases related to tax positions in a prior period		(75)	(82)	(32)
Gross increases related to tax positions in the current period		63	46	30
Settlements with taxing authorities		(45)	(22)	(2)
Lapse of statute of limitations		(4)	(12)	(3)
Balance at end of year		261	193	208
Unrecognized tax benefits would favorably impact the effective tax rate if recognized		$ 227	105	$ 116
Number of months of increase (decrease) in unrecognized tax benefit with respect to uncertain unrecognized tax positions (in months)		12
Accrued Interest and penalties in income tax provision		$ 36	$ 21
Interest and penalties included in income tax expense		3
Unrecorded deferred tax liability for temporary differences related to foreign subsidiaries		$ 89
Minimum [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, expiration dates		Jan. 01, 2016
Maximum [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, expiration dates		Dec. 31, 2033
U.S. Federal [Member]
Operating Loss Carryforwards [Line Items]
Deferred tax assets, operating loss carryforwards		$ 399
State [Member]
Operating Loss Carryforwards [Line Items]
Deferred tax assets, operating loss carryforwards		478
Non-U.S. [Member]
Operating Loss Carryforwards [Line Items]
Deferred tax assets, operating loss carryforwards		$ 476

[1] Upon the amendment and immediate exercise of the call option to acquire the remaining 55% ownership of Alliance Boots, the Company was required to compare the fair value of the amended option with the book value of the original option with a gain or loss recognized for the difference. The fair value of the amended option resulted in a financial statement loss of $866 million. The loss on the Alliance Boots call option was, in part, a capital loss and available to be carried forward and offset future capital gains through fiscal 2020. The loss was also the primary contributor to the 2014 valuation allowance amount reported in the deferred income tax table below. In 2015, the deferred tax asset related to the loss was recognized, resulting in the 4.1% effective tax rate benefit reported in the table above as well as a reduction to the valuation allowance amount reported in the deferred income tax table below.