Restructuring (Details) $ in Millions	3 Months Ended		9 Months Ended		21 Months Ended
	May 31, 2016 USD ($) Stores	May 31, 2015 USD ($)	May 31, 2016 USD ($) Stores	May 31, 2015 USD ($)	May 31, 2016 USD ($) Stores
Restructuring Reserve Disclosures [Abstract]
Pre-tax charges incurred during the period					$ 733
Total restructuring costs	$ 73	$ 160	$ 191	$ 177
Retail Pharmacy USA [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	60	151	170	168
Retail Pharmacy International [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	6	9	14	9
Pharmaceutical Wholesale [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	7	0	7	0
Real Estate Costs [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	0	24	52	41
Real Estate Costs [Member] | Retail Pharmacy USA [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	0	24	52	41
Real Estate Costs [Member] | Retail Pharmacy International [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	0	0	0	0
Real Estate Costs [Member] | Pharmaceutical Wholesale [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	0	0	0	0
Asset Impairments [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	48	102	73	102
Asset Impairments [Member] | Retail Pharmacy USA [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	48	102	73	102
Asset Impairments [Member] | Retail Pharmacy International [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	0	0	0	0
Asset Impairments [Member] | Pharmaceutical Wholesale [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	0	0	0	0
Severance and Other Business Transition and Exit Costs [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	25	34	66	34
Severance and Other Business Transition and Exit Costs [Member] | Retail Pharmacy USA [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	12	25	45	25
Severance and Other Business Transition and Exit Costs [Member] | Retail Pharmacy International [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	6	9	14	9
Severance and Other Business Transition and Exit Costs [Member] | Pharmaceutical Wholesale [Member]
Restructuring Reserve Disclosures [Abstract]
Total restructuring costs	$ 7	0	$ 7	0
Lease Termination Costs [Member]
Restructuring Reserve Disclosures [Abstract]
Pre-tax charges incurred during the period		0		17
Cost Transformation Program [Member]
Restructuring Reserve Disclosures [Abstract]
Number of stores planned to be closed | Stores	200		200		200
Pre-tax charges incurred during the period	$ 73	$ 160	$ 191	$ 160
Cost Transformation Program [Member] | Minimum [Member]
Restructuring Reserve Disclosures [Abstract]
Expected pre-tax charges	1,600		1,600		$ 1,600
Cost Transformation Program [Member] | Maximum [Member]
Restructuring Reserve Disclosures [Abstract]
Expected pre-tax charges	1,800		1,800		1,800
Cost Transformation Program [Member] | Real Estate Costs [Member]
Restructuring Reserve Disclosures [Abstract]
Pre-tax charges incurred during the period					254
Cost Transformation Program [Member] | Real Estate Costs [Member] | Minimum [Member]
Restructuring Reserve Disclosures [Abstract]
Expected pre-tax charges	525		525		525
Cost Transformation Program [Member] | Real Estate Costs [Member] | Maximum [Member]
Restructuring Reserve Disclosures [Abstract]
Expected pre-tax charges	600		600		600
Cost Transformation Program [Member] | Asset Impairments [Member]
Restructuring Reserve Disclosures [Abstract]
Pre-tax charges incurred during the period					296
Cost Transformation Program [Member] | Asset Impairments [Member] | Minimum [Member]
Restructuring Reserve Disclosures [Abstract]
Expected pre-tax charges	650		650		650
Cost Transformation Program [Member] | Asset Impairments [Member] | Maximum [Member]
Restructuring Reserve Disclosures [Abstract]
Expected pre-tax charges	725		725		725
Cost Transformation Program [Member] | Severance and Other Business Transition and Exit Costs [Member]
Restructuring Reserve Disclosures [Abstract]
Pre-tax charges incurred during the period					183
Cost Transformation Program [Member] | Severance and Other Business Transition and Exit Costs [Member] | Minimum [Member]
Restructuring Reserve Disclosures [Abstract]
Expected pre-tax charges	425		425		425
Cost Transformation Program [Member] | Severance and Other Business Transition and Exit Costs [Member] | Maximum [Member]
Restructuring Reserve Disclosures [Abstract]
Expected pre-tax charges	$ 475		$ 475		$ 475