Change in Accounting Policy (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		9 Months Ended		12 Months Ended
		May. 31, 2015	May. 31, 2014	May. 31, 2015	May. 31, 2014	Aug. 31, 2014	Feb. 28, 2015	Feb. 28, 2014	Aug. 31, 2013	Aug. 31, 2012
Consolidated Condensed Statements of Earnings [Abstract]
Equity earnings in Alliance Boots	[1]	$ 7	$ 137	$ 330	$ 467
Operating Income		1,401	1,024	3,832	3,208
Earnings Before Income Tax Provision		1,711	1,113	5,352	3,385
Income tax provision		408	357	1,120	1,167
Net Earnings		1,310	756	4,247	2,218
Net Earnings Attributable to Walgreens Boots Alliance, Inc.		$ 1,302	$ 714	$ 4,194	$ 2,153
Net earnings per common share attributable to Walgreens Boots Alliance, Inc. - basic (in dollars per share)		$ 1.19	$ 0.75	$ 4.08	$ 2.26
Net earnings per common share attributable to Walgreens Boots Alliance, Inc. - diluted (in dollars per share)		$ 1.18	$ 0.74	$ 4.04	$ 2.23
Consolidated Condensed Statements of Comprehensive Income [Abstract]
Net Earnings		$ 1,310	$ 756	$ 4,247	$ 2,218
Share of other comprehensive income (loss) of Alliance Boots		0	49	113	(7)
Cumulative translation adjustments		(149)	24	(639)	305
Total Other Comprehensive Income		(77)	98	(286)	364
Total Comprehensive Income		1,233	854	3,961	2,582
Comprehensive Income Attributable to Walgreens Boots Alliance, Inc.		1,229	812	3,917	2,517
Non-Current Assets [Abstract]
Equity investment in Alliance Boots		0		0		$ 7,336
Total Non-Current Assets		49,615		49,615		25,008
Total Assets		70,644		70,644		37,250
Non-Current Liabilities [Abstract]
Deferred income taxes		3,532		3,532		1,080
Total Non-Current Liabilities		22,558		22,558		7,738
Equity [Abstract]
Retained earnings		25,460		25,460		22,327
Accumulated other comprehensive income		(141)	272	(141)	272	136	$ (68)	$ 174	$ (92)
Total Walgreens Boots Alliance Inc. Shareholders' Equity		31,563		31,563		20,513
Total Equity		31,929		31,929		20,617
Total Liabilities and Equity		70,644		70,644		37,250
Cash Flows from Operating Activities [Abstract]
Net earnings		1,310	756	4,247	2,218
Deferred income taxes				240	219
Equity earnings in Alliance Boots	[1]	$ (7)	(137)	$ (330)	(467)
Reduction in non-current assets and non-current liabilities						(20)
Increase in retained earnings, net of tax						98
Alliance Boots [Member]
Change in Accounting Estimate [Line Items]
Percentage of initial interest (in hundredths)										45.00%
Consolidated Condensed Statements of Earnings [Abstract]
Equity earnings in Alliance Boots			135		465
Non-Current Assets [Abstract]
Equity investment in Alliance Boots						7,336
Cash Flows from Operating Activities [Abstract]
Equity earnings in Alliance Boots			(135)		(465)
As Reported [Member]
Consolidated Condensed Statements of Earnings [Abstract]
Operating Income			1,026		3,225
Earnings Before Income Tax Provision			1,115		3,402
Income tax provision			351		1,166
Net Earnings			764		2,236
Net Earnings Attributable to Walgreens Boots Alliance, Inc.			$ 722		$ 2,171
Net earnings per common share attributable to Walgreens Boots Alliance, Inc. - basic (in dollars per share)			$ 0.76		$ 2.28
Net earnings per common share attributable to Walgreens Boots Alliance, Inc. - diluted (in dollars per share)			$ 0.75		$ 2.25
Consolidated Condensed Statements of Comprehensive Income [Abstract]
Net Earnings			$ 764		$ 2,236
Share of other comprehensive income (loss) of Alliance Boots			(19)		(89)
Cumulative translation adjustments			69		323
Total Other Comprehensive Income			75		300
Total Comprehensive Income			839		2,536
Comprehensive Income Attributable to Walgreens Boots Alliance, Inc.			797		2,471
Non-Current Assets [Abstract]
Equity investment in Alliance Boots	[2]					7,248
Total Non-Current Assets	[2]					24,920
Total Assets	[2]					37,162
Non-Current Liabilities [Abstract]
Deferred income taxes	[2]					1,048
Total Non-Current Liabilities	[2]					7,706
Equity [Abstract]
Retained earnings	[2]					22,229
Accumulated other comprehensive income	[2]					178
Total Walgreens Boots Alliance Inc. Shareholders' Equity	[2]					20,457
Total Equity	[2]					20,561
Total Liabilities and Equity	[2]					37,162
Cash Flows from Operating Activities [Abstract]
Net earnings			764		2,236
Deferred income taxes					218
As Reported [Member] | Alliance Boots [Member]
Consolidated Condensed Statements of Earnings [Abstract]
Equity earnings in Alliance Boots			137		482
Cash Flows from Operating Activities [Abstract]
Equity earnings in Alliance Boots			(137)		(482)
Adjustments [Member]
Consolidated Condensed Statements of Earnings [Abstract]
Operating Income			(2)		(17)
Earnings Before Income Tax Provision			(2)		(17)
Income tax provision			6		1
Net Earnings			(8)		(18)
Net Earnings Attributable to Walgreens Boots Alliance, Inc.			$ (8)		$ (18)
Net earnings per common share attributable to Walgreens Boots Alliance, Inc. - basic (in dollars per share)			$ (0.01)		$ (0.02)
Net earnings per common share attributable to Walgreens Boots Alliance, Inc. - diluted (in dollars per share)			$ (0.01)		$ (0.02)
Consolidated Condensed Statements of Comprehensive Income [Abstract]
Net Earnings			$ (8)		$ (18)
Share of other comprehensive income (loss) of Alliance Boots			68		82
Cumulative translation adjustments			(45)		(18)
Total Other Comprehensive Income			23		64
Total Comprehensive Income			15		46
Comprehensive Income Attributable to Walgreens Boots Alliance, Inc.			15		46
Non-Current Assets [Abstract]
Equity investment in Alliance Boots						88
Total Non-Current Assets						88
Total Assets						88
Non-Current Liabilities [Abstract]
Deferred income taxes						32
Total Non-Current Liabilities						32
Equity [Abstract]
Retained earnings						98
Accumulated other comprehensive income						(42)
Total Walgreens Boots Alliance Inc. Shareholders' Equity						56
Total Equity						56
Total Liabilities and Equity						$ 88
Cash Flows from Operating Activities [Abstract]
Net earnings			(8)		(18)
Deferred income taxes					1
Adjustments [Member] | Alliance Boots [Member]
Consolidated Condensed Statements of Earnings [Abstract]
Equity earnings in Alliance Boots			(2)		(17)
Cash Flows from Operating Activities [Abstract]
Equity earnings in Alliance Boots			$ 2		$ 17

[1] Alliance Boots became a consolidated subsidiary and ceased being accounted for under the equity method upon completion of the Second Step Transaction on December 31, 2014. Earnings for the three and nine month periods ended May 31, 2015 reflect incremental acquisition-related amortization expense of zero and $14 million ($11 million net of tax), respectively. Incremental acquisition-related amortization expense for the three and nine month periods ended May 31, 2014 were $11 million ($9 million net of tax) and $31 million ($25 million net of tax), respectively. Earnings in foreign equity method investments are translated at their respective average exchange rates.

[2] Due to the adoption of Accounting Standards Update 2015-03, Interest - Imputation of Interest, all reported periods include debt issuance costs as a contra-liability. This impacts the August 31, 2014 Consolidated Condensed Balance Sheet by reducing non-current assets and non-current liabilities by $20 million.