Goodwill and other intangible assets - schedule of goodwill (Details) - USD ($) $ in Millions	12 Months Ended
Aug. 31, 2019	Aug. 31, 2018
Goodwill [Roll Forward]
Beginning balance	$ 16,914	$ 15,632
Acquisitions	8	1,348
Dispositions	(9)
Currency translation adjustments	(353)	(66)
Ending balance	16,560	16,914
Operating Segments \| Retail Pharmacy USA
Goodwill [Roll Forward]
Beginning balance	10,483	9,139
Acquisitions	8	1,344
Dispositions	0
Currency translation adjustments	0	0
Ending balance	10,491	10,483
Operating Segments \| Retail Pharmacy International
Goodwill [Roll Forward]
Beginning balance	3,370	3,392
Acquisitions	0	0
Dispositions	(9)
Currency translation adjustments	(182)	(22)
Ending balance	3,179	3,370
Operating Segments \| Pharmaceutical Wholesale
Goodwill [Roll Forward]
Beginning balance	3,061	3,101
Acquisitions	0	4
Dispositions	0
Currency translation adjustments	(171)	(44)
Ending balance	$ 2,890	$ 3,061

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

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Amount of foreign currency translation gain (loss) which increases (decreases) an asset representing future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of divestiture of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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