Restructuring (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		23 Months Ended
	Feb. 28, 2017	Feb. 29, 2016	Feb. 28, 2017	Feb. 29, 2016	Feb. 28, 2017
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	$ 340	$ 28	$ 421	$ 118
Asset impairments
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	67	0	115	25
Real estate costs
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	240	0	249	52
Severance and other business transition and exit costs
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	33	28	57	41
Cost Transformation Program
Restructuring Reserve Disclosures [Abstract]
Pre-tax charges incurred during the period					$ 1,400
Restructuring Reserve [Roll Forward]
Beginning Balance			275
Restructuring Costs			421
Payments			(57)
Other - non cash			(128)
Currency translation adjustments			(1)
Ending Balance	510		510		510
Cost Transformation Program | Asset impairments
Restructuring Reserve Disclosures [Abstract]
Pre-tax charges incurred during the period					563
Restructuring Reserve [Roll Forward]
Beginning Balance			0
Restructuring Costs			115
Payments			0
Other - non cash			(115)
Currency translation adjustments			0
Ending Balance	0		0		0
Cost Transformation Program | Real estate costs
Restructuring Reserve Disclosures [Abstract]
Pre-tax charges incurred during the period					542
Restructuring Reserve [Roll Forward]
Beginning Balance			248
Restructuring Costs			249
Payments			(28)
Other - non cash			0
Currency translation adjustments			0
Ending Balance	469		469		469
Cost Transformation Program | Severance and other business transition and exit costs
Restructuring Reserve Disclosures [Abstract]
Pre-tax charges incurred during the period					282
Restructuring Reserve [Roll Forward]
Beginning Balance			27
Restructuring Costs			57
Payments			(29)
Other - non cash			(13)
Currency translation adjustments			(1)
Ending Balance	41		41		$ 41
Reportable Segments | Retail Pharmacy USA
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	316	25	388	110
Reportable Segments | Retail Pharmacy USA | Asset impairments
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	65	0	111	25
Reportable Segments | Retail Pharmacy USA | Real estate costs
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	240	0	249	52
Reportable Segments | Retail Pharmacy USA | Severance and other business transition and exit costs
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	11	25	28	33
Reportable Segments | Retail Pharmacy International
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	19	3	25	8
Reportable Segments | Retail Pharmacy International | Asset impairments
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	1	0	3	0
Reportable Segments | Retail Pharmacy International | Real estate costs
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	0	0	0	0
Reportable Segments | Retail Pharmacy International | Severance and other business transition and exit costs
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	18	3	22	8
Reportable Segments | Pharmaceutical Wholesale
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	5	0	8	0
Reportable Segments | Pharmaceutical Wholesale | Asset impairments
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	1	0	1	0
Reportable Segments | Pharmaceutical Wholesale | Real estate costs
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	0	0	0	0
Reportable Segments | Pharmaceutical Wholesale | Severance and other business transition and exit costs
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	$ 4	$ 0	$ 7	$ 0