Segment Reporting (Details) $ in Millions			12 Months Ended
		Dec. 31, 2014 Segment	Aug. 31, 2016 USD ($) Segment Customer	Aug. 31, 2015 USD ($) Customer	Aug. 31, 2014 USD ($)
Segment Reporting [Abstract]
Number of reportable segments | Segment		3	3
Segment Reporting Information [Line Items]
Number of customers | Customer			0
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales			$ 117,351	$ 103,444	$ 76,392
Adjusted Operating Income			7,208	6,157	4,866
Depreciation and amortization			1,718	1,742	1,316
Additions to property, plant and equipment			1,325	1,251	1,106
Cost transformation			(424)	(542)
Acquisition-related amortization			(369)	(485)	(282)
LIFO provision			(214)	(285)	(132)
Acquisition-related costs			(102)	(87)	(82)
Legal settlement			(47)
Asset impairment			(30)	(110)
Store closures and other optimization costs				(56)	(271)
Gain (loss) on sale of business				(17)	9
Adjustments to equity earnings in AmerisourceBergen			(21)
Adjustments to equity earnings in Alliance Boots				93	86
Operating Income			6,001	$ 4,668	4,194
Walgreens Boots Alliance [Member]
Segment Reporting Information [Line Items]
Ownership percentage of WBA		55.00%
Alliance Boots [Member]
Segment Reporting Information [Line Items]
Equity interest in Alliance Boots		45.00%		45.00%
Retail Pharmacy USA [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales			$ 83,802	$ 80,974	76,392
Retail Pharmacy USA [Member] | Revenues [Member]
Segment Reporting Information [Line Items]
Number of customers | Customer			2	1
Concentration risk			22.00%	12.00%
Retail Pharmacy International [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	[1]		$ 13,256	$ 8,657	0
Retail Pharmacy International [Member] | Revenues [Member]
Segment Reporting Information [Line Items]
Number of customers | Customer			1
Concentration risk			18.00%	20.00%
Pharmaceutical Wholesale [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales			$ 22,571	$ 15,327	0
Reportable Segments [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales			117,351	103,444	76,392
Reportable Segments [Member] | Retail Pharmacy USA [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales			83,802	80,974	76,392
Adjusted Operating Income			5,357	5,098	4,866
Depreciation and amortization			1,134	1,217	1,316
Additions to property, plant and equipment			777	951	1,106
Reportable Segments [Member] | Retail Pharmacy International [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	[1]		13,256	8,657	0
Adjusted Operating Income	[1]		1,155	616	0
Depreciation and amortization	[1]		401	393	0
Additions to property, plant and equipment	[1]		444	249	0
Reportable Segments [Member] | Pharmaceutical Wholesale [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales			20,293	13,813	0
Adjusted Operating Income			708	450	0
Depreciation and amortization			166	120	0
Additions to property, plant and equipment			104	51	0
Intersegment Eliminations [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	[1]		(2,278)	(1,514)	0
Adjusted Operating Income	[1]		(12)	(7)	0
Depreciation and amortization	[1]		17	12	0
Additions to property, plant and equipment	[1]		0	0	0
Intersegment Eliminations [Member] | Retail Pharmacy USA [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales			0	0	0
Intersegment Eliminations [Member] | Retail Pharmacy International [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales	[1]		0	0	0
Intersegment Eliminations [Member] | Pharmaceutical Wholesale [Member]
Segment Reporting Information, Operating Income (Loss) [Abstract]
Sales			$ 2,278	$ 1,514	$ 0

[1] To improve comparability, certain classification changes have been made to fiscal 2015 Sales, Cost of sales and Selling, general and administrative expenses. This change has no impact on Operating Income.