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Number of shares of affiliates held for management investment companies.

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Equity method investments - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Nov. 30, 2017	Nov. 30, 2016	Aug. 31, 2017
Schedule of Equity Method Investments [Line Items]
Equity earnings (losses)	$ (99)	$ 29
AmerisourceBergen
Schedule of Equity Method Investments [Line Items]
Outstanding shares owned (in shares)	56,854,867		56,854,867
Ownership percentage	26.00%		26.00%
Period of reporting lag	2 months
Equity investment, exceeded its proportionate share of net assets	$ 4,400
AmerisourceBergen \| Level 1
Schedule of Equity Method Investments [Line Items]
Fair market value of equity investment	4,800
Other Investments
Schedule of Equity Method Investments [Line Items]
Equity earnings (losses)	13	$ 12
Other than temporary impairment	$ 170