Segment reporting - results of operations of reportable segments (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Aug. 31, 2021	May 31, 2021	Feb. 28, 2021	Nov. 30, 2020	Aug. 31, 2020	May 31, 2020	Feb. 29, 2020	Nov. 30, 2019	Aug. 31, 2021	Aug. 31, 2020	Aug. 31, 2019
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	$ 34,262	$ 34,030	$ 32,779	$ 31,438	$ 30,371	$ 30,364	$ 31,336	$ 29,912	$ 132,509	$ 121,982	$ 120,074
Adjusted operating income									5,117	4,730	6,481
Depreciation and amortization									1,923	1,786	1,894
Capital expenditures									1,312	1,287	1,598
Adjustments to equity earnings (loss) in AmerisourceBergen									(1,645)	(97)	(233)
Transformational cost management									(417)	(719)	(327)
Acquisition-related amortization									(523)	(384)	(416)
Certain legal and regulatory accruals and settlements									(75)	0	(31)
LIFO provision									(13)	(95)	(136)
Acquisition-related costs									(54)	(315)	(303)
Impairment of goodwill and intangible assets									(49)	(2,016)	(73)
Store optimization									0	(53)	(196)
Store damage and inventory losses									0	(68)	0
Operating income									2,342	982	4,766
Reportable Segments | United States
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales									112,005	107,701	104,532
Adjusted operating income									5,019	4,761	5,873
Depreciation and amortization									1,513	1,376	1,454
Capital expenditures									1,030	1,040	1,318
Reportable Segments | International
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales									20,505	14,281	15,542
Adjusted operating income									466	157	759
Depreciation and amortization									399	400	433
Capital expenditures									243	235	272
Corporate and Other
Segment Reporting Information, Operating Income (Loss) [Abstract]
Adjusted operating income									(368)	(187)	(152)
Depreciation and amortization									11	10	8
Capital expenditures									$ 39	$ 12	$ 8