Segment Reporting (Details) $ in Millions	3 Months Ended		9 Months Ended
	May. 31, 2015 USD ($)	May. 31, 2014 USD ($)	May. 31, 2015 USD ($) Segment	May. 31, 2014 USD ($)	Aug. 31, 2014 USD ($)
Segment Reporting [Abstract]
Number of reportable segments | Segment			3
Equity interest in Alliance Boots (in hundredths)	45.00%		45.00%
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	$ 28,795	$ 19,401	$ 74,922	$ 57,335
Cost of sales	21,314	13,961	55,263	41,093
Gross Profit	7,481	5,440	19,659	16,242
Selling, general and administrative expenses	6,080	4,551	16,142	13,499
Equity earnings in Alliance Boots	0	135	315	465
Operating Income	1,401	1,024	3,832	3,208
Total assets	70,644		70,644		$ 37,250
Segment Reporting Information, Income (Loss) before Income Taxes [Abstract]
Operating Income	1,401	1,024	3,832	3,208
Gain on previously held equity interest	0	0	706	0
Other income	461	124	1,164	290
Earnings Before Interest and Income Tax Provision	1,862	1,148	5,702	3,498
Retail Pharmacy USA [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	20,425	19,401	61,027	57,335
Retail Pharmacy International [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	3,268	0	5,315	0
Pharmaceutical Wholesale [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	5,708	0	9,573	0
Eliminations and Unallocated Items [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	(606)	0	(993)	0
Cost of sales	(607)	0	(990)	0
Gross Profit	1	0	(3)	0
Selling, general and administrative expenses	0	0	0	0
Equity earnings in Alliance Boots		0	0	0
Operating Income	1	0	(3)	0
Total assets	(6,627)		(6,627)		(7,005)
Segment Reporting Information, Income (Loss) before Income Taxes [Abstract]
Operating Income	1	0	(3)	0
Reportable Segments [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	28,795	19,401	74,922	57,335
Cost of sales	21,314	13,961	55,263	41,093
Gross Profit	7,481	5,440	19,659	16,242
Selling, general and administrative expenses	6,080	4,551	16,142	13,499
Equity earnings in Alliance Boots		135	315	465
Operating Income	1,401	1,024	3,832	3,208
Total assets	70,644		70,644		37,250
Segment Reporting Information, Income (Loss) before Income Taxes [Abstract]
Operating Income	1,401	1,024	3,832	3,208
Gain on previously held equity interest	0	0	706	0
Other income	461	124	1,164	290
Earnings Before Interest and Income Tax Provision	1,862	1,148	5,702	3,498
Reportable Segments [Member] | Retail Pharmacy USA [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	20,425	19,401	61,027	57,335
Cost of sales	14,898	13,961	44,458	41,093
Gross Profit	5,527	5,440	16,569	16,242
Selling, general and administrative expenses	4,494	4,551	13,505	13,499
Equity earnings in Alliance Boots		135	315	465
Operating Income	1,033	1,024	3,379	3,208
Total assets	41,714		41,714		44,255
Segment Reporting Information, Income (Loss) before Income Taxes [Abstract]
Operating Income	1,033	1,024	3,379	3,208
Reportable Segments [Member] | Retail Pharmacy International [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	3,231	0	5,248	0
Cost of sales	1,875	0	3,169	0
Gross Profit	1,393	0	2,146	0
Selling, general and administrative expenses	1,188	0	1,933	0
Equity earnings in Alliance Boots		0	0	0
Operating Income	205	0	213	0
Total assets	22,514		22,514		0
Segment Reporting Information, Income (Loss) before Income Taxes [Abstract]
Operating Income	205	0	213	0
Reportable Segments [Member] | Pharmaceutical Wholesale [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	5,139	0	8,647	0
Cost of sales	5,148	0	8,626	0
Gross Profit	560	0	947	0
Selling, general and administrative expenses	398	0	704	0
Equity earnings in Alliance Boots		0	0	0
Operating Income	162	0	243	0
Total assets	13,043		13,043		$ 0
Segment Reporting Information, Income (Loss) before Income Taxes [Abstract]
Operating Income	162	0	243	0
Reportable Segments [Member] | Eliminations and Unallocated Items [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	0	0	0	0
Operating Income	1	0	(3)	0
Segment Reporting Information, Income (Loss) before Income Taxes [Abstract]
Operating Income	1	0	(3)	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	37	0	67	0
Intersegment Eliminations [Member] | Pharmaceutical Wholesale [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	569	0	926	0
Intersegment Eliminations [Member] | Eliminations and Unallocated Items [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	$ (606)	$ 0	$ (993)	$ 0