The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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Goodwill and other intangible assets - additional information (Details) - USD ($) $ in Millions	12 Months Ended
	Aug. 31, 2017	Aug. 31, 2016	Aug. 31, 2015	Mar. 31, 2017	Dec. 31, 2014
Goodwill [Line Items]
Goodwill	$ 15,632	$ 15,527	$ 16,372
Goodwill removed due to sale of business		4
Amortization expense for intangible assets	$ 385	$ 396	$ 480
Alliance Boots
Goodwill [Line Items]
Goodwill					$ 14,861
Intangible assets					11,691
AllianceRx Walgreens Prime
Goodwill [Line Items]
Goodwill				$ 103
Intangible assets				$ 331
Minimum
Goodwill [Line Items]
Reporting unit fair value in excess of carrying amount (as a percent)	9.00%
Maximum
Goodwill [Line Items]
Reporting unit fair value in excess of carrying amount (as a percent)	400.00%
Retail Pharmacy International \| Alliance Boots
Goodwill [Line Items]
Reporting unit fair value in excess of carrying amount (as a percent)	9.00%
Goodwill					$ 3,900