Segment Reporting (Details) $ in Millions	3 Months Ended		9 Months Ended
	May 31, 2016 USD ($)	May 31, 2015 USD ($)	May 31, 2016 USD ($) Segment	May 31, 2015 USD ($)	Dec. 31, 2014
Segment Reporting [Abstract]
Number of reportable segments | Segment			3
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	$ 29,498	$ 28,795	$ 88,715	$ 74,922
Operating Income	1,533	1,401	4,861	3,832
Increase in fair market value of AmerisourceBergen warrants				(123)
Acquisition-related amortization	100	96	282	402
LIFO provision	93	69	191	176
Cost transformation	73	160	207	160
Acquisition-related costs	15	4	82	87
Asset impairment			30	110
Store closures and other optimization costs		7		51
Loss on sale of business		12		12
Adjusted Operating Income	$ 1,814	1,749	$ 5,653	4,707
Alliance Boots [Member]
Segment Reporting Information [Line Items]
Equity interest in Alliance Boots	45.00%		45.00%		45.00%
Walgreens Boots Alliance [Member]
Segment Reporting Information [Line Items]
Ownership percentage of WBA					55.00%
Retail Pharmacy USA [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	$ 21,185	20,425	$ 63,055	61,027
Adjusted Operating Income	1,382	1,328	4,257	4,044
Retail Pharmacy International [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	3,194	3,268	10,414	5,315
Adjusted Operating Income	258	249	908	374
Pharmaceutical Wholesale [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	5,748	5,708	17,171	9,573
Adjusted Operating Income	179	171	500	292
Eliminations and Unallocated Items [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	(629)	(606)	(1,925)	(993)
Adjusted Operating Income	(5)	1	(12)	(3)
Reportable Segments [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	29,498	28,795	88,715	74,922
Adjusted Operating Income	1,814	1,749	5,653	4,707
Reportable Segments [Member] | Retail Pharmacy USA [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	21,185	20,425	63,055	61,027
Adjusted Operating Income	1,382	1,328	4,257	4,044
Reportable Segments [Member] | Retail Pharmacy International [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	3,132	3,231	10,218	5,248
Adjusted Operating Income	258	249	908	374
Reportable Segments [Member] | Pharmaceutical Wholesale [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	5,181	5,139	15,442	8,647
Adjusted Operating Income	179	171	500	292
Reportable Segments [Member] | Eliminations and Unallocated Items [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	0	0	0	0
Intersegment Eliminations [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	0	0	0	0
Intersegment Eliminations [Member] | Retail Pharmacy USA [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	0	0	0	0
Intersegment Eliminations [Member] | Retail Pharmacy International [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	62	37	196	67
Intersegment Eliminations [Member] | Pharmaceutical Wholesale [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	567	569	1,729	926
Intersegment Eliminations [Member] | Eliminations and Unallocated Items [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	$ (629)	$ (606)	$ (1,925)	$ (993)