Goodwill and other intangible assets - Schedule of Goodwill (Details) $ in Millions	9 Months Ended
May 31, 2018 USD ($)
Goodwill [Roll Forward]
Net book value - Beginning Period	$ 15,632
Acquisitions	1,365
Currency translation adjustments	92
Net book value - Ending Period	17,089
Retail Pharmacy USA
Goodwill [Roll Forward]
Net book value - Beginning Period	9,139
Acquisitions	1,361
Currency translation adjustments	0
Net book value - Ending Period	10,500
Retail Pharmacy International
Goodwill [Roll Forward]
Net book value - Beginning Period	3,392
Acquisitions	0
Currency translation adjustments	54
Net book value - Ending Period	3,446
Pharmaceutical Wholesale
Goodwill [Roll Forward]
Net book value - Beginning Period	3,101
Acquisitions	4
Currency translation adjustments	38
Net book value - Ending Period	$ 3,143

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.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975

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- Definition

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.

+ References

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- Definition

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.

+ References

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- Definition

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

+ References

No definition available.

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