Depreciation and amortization (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Feb. 28, 2018	Feb. 28, 2017	Feb. 28, 2018	Feb. 28, 2017
Depreciation, Depletion and Amortization [Abstract]
Depreciation expense	$ 347	$ 332	$ 682	$ 666
Intangible asset and other amortization	95	81	176	165
Total depreciation and amortization expense	$ 442	$ 413	$ 858	$ 831

The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

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- References

No definition available.

+ Details

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- Definition

The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.

+ References

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- Definition

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. The aggregate amount of recurring noncash expense charged against earnings in the period to allocate the cost of assets over their estimated remaining economic lives.

+ References

No definition available.

+ Details

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