Income taxes - deferred tax assets and liabilities (Details) - USD ($) $ in Millions	Aug. 31, 2019	Aug. 31, 2018
Deferred tax assets:
Compensation and benefits	$ 133	$ 152
Insurance	90	74
Accrued rent	219	271
Allowance for doubtful accounts	13	27
Tax attributes	6,687	2,351
Stock compensation	45	44
Deferred income	115	110
Other	78	44
Subtotal deferred tax assets	7,380	3,073
Less: valuation allowance	6,638	2,226
Total deferred tax assets	742	847
Deferred tax liabilities:
Accelerated depreciation	475	603
Inventory	394	301
Intangible assets	1,116	1,234
Equity method investment	481	459
Total deferred tax liabilities	2,466	2,597
Net deferred tax liabilities	$ 1,724	$ 1,750