Acquisitions - Schedule of consideration (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Feb. 28, 2018	Feb. 28, 2018	Aug. 31, 2017
Business Acquisition [Line Items]
Goodwill	$ 17,017	$ 17,017	$ 15,632
AllianceRx Walgreens Prime
Business Acquisition [Line Items]
Consideration		720
Accounts receivable	217	217
Inventories	149	149
Property, plant and equipment	11	11
Intangible assets	331	331
Trade accounts payable	(90)	(90)
Accrued expenses and other liabilities	(1)	(1)
Total identifiable net assets	617	617
Goodwill	103	103
Rite Aid Corporation
Business Acquisition [Line Items]
Consideration	3,100	3,509
Inventories	998	998
Property, plant and equipment	431	431
Intangible assets	1,624	1,624
Accrued expenses and other liabilities	(41)	(41)
Deferred income taxes	3	3
Other non-current liabilities	(516)	(516)
Total identifiable net assets	2,499	2,499
Goodwill	$ 1,010	$ 1,010