Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($)				12 Months Ended
	Aug. 31, 2016	Aug. 31, 2015	Aug. 31, 2014	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Schedule Of Other Intangible Assets [Line Items]
Goodwill impairment	$ 0	$ 0	$ 0
Amortization expense for intangible assets				$ 15,400,000	$ 13,500,000	$ 11,500,000