Goodwill and other intangible assets - Schedule of Goodwill (Details) $ in Millions	9 Months Ended
May 31, 2020 USD ($)
Goodwill [Roll Forward]
Net book value - Beginning Period	$ 16,560
Acquisitions	63
Impairment	(1,675)
Currency translation adjustments	0
Net book value - Ending Period	14,948
Reportable Segments \| Retail Pharmacy USA
Goodwill [Roll Forward]
Net book value - Beginning Period	10,491
Acquisitions	63
Impairment	0
Currency translation adjustments	0
Net book value - Ending Period	10,554
Reportable Segments \| Retail Pharmacy International
Goodwill [Roll Forward]
Net book value - Beginning Period	3,179
Acquisitions	0
Impairment	(1,675)
Currency translation adjustments	(9)
Net book value - Ending Period	1,495
Reportable Segments \| Pharmaceutical Wholesale
Goodwill [Roll Forward]
Net book value - Beginning Period	2,890
Acquisitions	0
Impairment	0
Currency translation adjustments	9
Net book value - Ending Period	$ 2,900

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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