Derivative Financial Instruments and Hedging Activities - Additional Information (Detail) (USD $)	3 Months Ended			9 Months Ended
	May 31, 2012	May 31, 2011	Aug. 31, 2007	May 31, 2012	May 31, 2011	Aug. 31, 2011	Feb. 28, 2011
Derivative [Line Items]
Aggregate notional amount outstanding of foreign currency denominated revenues and expenses designated as cash flow hedges	$ 178,800,000	$ 176,000,000		$ 178,800,000	$ 176,000,000
Aggregate notional amount outstanding of forward contracts to hedge transactional exposure	874,100,000	686,900,000		874,100,000	686,900,000
Amount estimated to reclassify into earnings during the next 12 months related to foreign currency risk management hedging arrangements	700,000			700,000
Notional amount of interest rate swaps designated as fair value hedges							200,000,000
Interest expenses	26,462,000	25,149,000		78,303,000	73,088,000
Hedge accounting adjustment related to terminated interest rate swaps	9,790,000			9,790,000		11,570,000
Notional amount of interest rate swaps designated as cash flow hedges			400,000,000
Payment to settle interest rate swaps			43,100,000
Amount estimated to reclassify into earnings during the next 12 months related to interest rate risk management hedging arrangements	4,000,000			4,000,000
8.250% Senior Notes Due 2018
Derivative [Line Items]
Senior unsecured notes, terminated interest rate	8.25%		8.25%	8.25%		8.25%
Expiry date			Mar. 15, 2018
7.750% Senior Notes Due 2016
Derivative [Line Items]
Senior unsecured notes, terminated interest rate	7.75%			7.75%		7.75%	7.75%
Fair value adjustment related to interest rate swap including accrued interest on interest rate swaps						12,200,000
Accrued interest on interest rate swaps						600,000
Interest rate swap
Derivative [Line Items]
Interest expenses	$ 600,000			$ 1,800,000