Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($)				12 Months Ended
Aug. 31, 2019	Aug. 31, 2018	Aug. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill impairment	$ 0	$ 0	$ 0
Amortization expense for intangible assets				$ 19,400,000	$ 19,600,000	$ 16,700,000

Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13777-109266

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