Acquisitions - Schedule of consideration (Details) - USD ($) $ in Millions		3 Months Ended	9 Months Ended
	Mar. 31, 2017	May 31, 2018	May 31, 2018	Aug. 31, 2017
Business Acquisition [Line Items]
Goodwill		$ 17,089	$ 17,089	$ 15,632
AllianceRx Walgreens Prime
Business Acquisition [Line Items]
Consideration	$ 720
Accounts receivable	217
Inventories	149
Property, plant and equipment	11
Intangible assets	331
Trade accounts payable	(90)
Accrued expenses and other liabilities	(1)
Total identifiable net assets	617
Goodwill	$ 103
Rite Aid Corporation
Business Acquisition [Line Items]
Consideration		820	4,330
Inventories		1,291	1,291
Property, plant and equipment		494	494
Intangible assets		2,028	2,028
Accrued expenses and other liabilities		(54)	(54)
Deferred income taxes		5	5
Other non-current liabilities		(795)	(795)
Total identifiable net assets		2,969	2,969
Goodwill		$ 1,361	$ 1,361