Leases - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Aug. 31, 2012	Aug. 31, 2011	Aug. 31, 2010
Operating Leased Assets [Line Items]
Rental expense under operating leases, net	$ 6.0	$ 5.4	$ 6.0
Sublease rental income			$ 0.1
Minimum [Member] | Vehicles And Office Equipment [Member]
Operating Leased Assets [Line Items]
Operating lease term (in years)	1 year
Minimum [Member] | Real Estate Leases [Member]
Operating Leased Assets [Line Items]
Operating lease term (in years)	5 years
Maximum [Member] | Vehicles And Office Equipment [Member]
Operating Leased Assets [Line Items]
Operating lease term (in years)	15 years
Maximum [Member] | Real Estate Leases [Member]
Operating Leased Assets [Line Items]
Operating lease term (in years)	20 years