Exit and disposal activities - Restructuring Costs (Details) - Footprint Optimization Program $ in Millions	3 Months Ended
	Nov. 30, 2024 USD ($)
Operating Segments | U.S. Retail Pharmacy
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 323
Operating Segments | International
Restructuring Cost and Reserve [Line Items]
Restructuring costs	3
Operating Segments | U.S. Healthcare
Restructuring Cost and Reserve [Line Items]
Restructuring costs	4
Corporate and Other
Restructuring Cost and Reserve [Line Items]
Restructuring costs	3
Lease obligations and other real estate costs | Operating Segments | U.S. Retail Pharmacy
Restructuring Cost and Reserve [Line Items]
Restructuring costs	163
Lease obligations and other real estate costs | Operating Segments | International
Restructuring Cost and Reserve [Line Items]
Restructuring costs	1
Lease obligations and other real estate costs | Operating Segments | U.S. Healthcare
Restructuring Cost and Reserve [Line Items]
Restructuring costs	0
Lease obligations and other real estate costs | Corporate and Other
Restructuring Cost and Reserve [Line Items]
Restructuring costs	0
Asset impairments | Operating Segments | U.S. Retail Pharmacy
Restructuring Cost and Reserve [Line Items]
Restructuring costs	125
Asset impairments | Operating Segments | International
Restructuring Cost and Reserve [Line Items]
Restructuring costs	1
Asset impairments | Operating Segments | U.S. Healthcare
Restructuring Cost and Reserve [Line Items]
Restructuring costs	1
Asset impairments | Corporate and Other
Restructuring Cost and Reserve [Line Items]
Restructuring costs	0
Employee severance and other exit costs | Operating Segments | U.S. Retail Pharmacy
Restructuring Cost and Reserve [Line Items]
Restructuring costs	34
Employee severance and other exit costs | Operating Segments | International
Restructuring Cost and Reserve [Line Items]
Restructuring costs	1
Employee severance and other exit costs | Operating Segments | U.S. Healthcare
Restructuring Cost and Reserve [Line Items]
Restructuring costs	3
Employee severance and other exit costs | Corporate and Other
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 3