Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	Aug. 31, 2017	Aug. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Outstanding letters of credit	$ 14.5	$ 17.8
Discounted present value of future minimum lease payments	$ 13.5
Weighted Average Discount Rate on Future Minimum Lease Payments	2.29%
Electrical
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discounted present value of future minimum lease payments	$ 10.7