Segment reporting (Details) $ in Millions	3 Months Ended		6 Months Ended
	Feb. 28, 2019 USD ($)	Feb. 28, 2018 USD ($)	Feb. 28, 2019 USD ($) segment	Feb. 28, 2018 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment			3
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	$ 34,528	$ 33,021	$ 68,321	$ 63,761
Adjusted operating income	1,935	2,160	3,667	3,966
Acquisition-related amortization	(123)	(113)	(246)	(198)
Transformational cost management	(150)		(179)
Acquisition-related costs	(82)	(65)	(148)	(116)
Adjustments to equity earnings in AmerisourceBergen	(9)	113	(54)	(76)
Store optimization	(31)		(51)
LIFO provision	(8)	(43)	(48)	(97)
Certain legal and regulatory accruals and settlements	(14)	(90)	(24)	(115)
LIFO provision				(83)
Asset recovery		15		15
Operating income	1,517	1,977	2,918	3,296
Reportable Segments | Retail Pharmacy USA
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	26,257	24,478	51,979	46,967
Adjusted operating income	1,455	1,650	2,834	3,028
Reportable Segments | Retail Pharmacy International
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	3,082	3,317	5,982	6,400
Adjusted operating income	256	276	388	481
Reportable Segments | Pharmaceutical Wholesale
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	5,738	5,755	11,446	11,473
Adjusted operating income	225	231	445	456
Eliminations
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	(549)	(529)	(1,086)	(1,079)
Adjusted operating income	$ (1)	$ 3	0	$ 1
November 30, 2017 Legal And Regulatory Accruals And Settlements
Segment Reporting Information, Operating Income (Loss) [Abstract]
Adjustments to financial statements to present non-GAAP measures			14
February 28, 2018 Legal And Regulatory Accruals And Settlements
Segment Reporting Information, Operating Income (Loss) [Abstract]
Adjustments to financial statements to present non-GAAP measures			50
May 31, 2018 Legal And Regulatory Accruals And Settlements
Segment Reporting Information, Operating Income (Loss) [Abstract]
Adjustments to financial statements to present non-GAAP measures			$ 5