Segment reporting (Details) $ in Millions	3 Months Ended		9 Months Ended
	May 31, 2021 USD ($) segment	May 31, 2020 USD ($)	May 31, 2021 USD ($) segment	May 31, 2020 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment	2		2
Sales	$ 34,030	$ 30,364	$ 98,247	$ 91,612
Adjusted operating income	1,459	798	3,881	3,724
Adjustments to equity earnings (loss) in AmerisourceBergen	(48)	105	(1,575)	(47)
Transformational cost management	(60)	(310)	(338)	(508)
Acquisition-related amortization	(158)	(94)	(367)	(290)
Certain legal and regulatory accruals and settlements	0	0	(60)	0
LIFO provision	(51)	(29)	(85)	(90)
Acquisition-related costs	(9)	(68)	(25)	(291)
Impairment of goodwill and intangible assets	0	(2,001)	0	(2,001)
Store optimization	0	(10)	0	(49)
Store damage and inventory losses	0	(75)	0	(75)
Operating income (loss)	1,134	(1,683)	1,432	374
Reportable Segments | United States
Segment Reporting Information [Line Items]
Sales	28,743	27,357	83,250	80,734
Adjusted operating income	1,471	979	3,789	3,704
Reportable Segments | International
Segment Reporting Information [Line Items]
Sales	5,288	3,008	14,998	10,878
Adjusted operating income	94	(135)	326	155
Corporate and Other
Segment Reporting Information [Line Items]
Adjusted operating income	$ (105)	$ (46)	$ (233)	$ (135)