Summary of Outstanding Forward Foreign Currency Contracts, by Currency (Detail) (Not Designated as Hedging Instrument) In Thousands, unless otherwise specified	Mar. 31, 2012 Foreign Exchange Contracts to Sell Canadian Dollar for US Dollar USD ($)	Mar. 31, 2012 Foreign Exchange Contracts to Sell Canadian Dollar for US Dollar CAD	Sep. 30, 2011 Foreign Exchange Contracts to Sell Canadian Dollar for US Dollar USD ($)	Sep. 30, 2011 Foreign Exchange Contracts to Sell Canadian Dollar for US Dollar CAD	Mar. 31, 2012 Foreign Exchange Contracts To Sell European Euro for US Dollar USD ($)	Mar. 31, 2012 Foreign Exchange Contracts To Sell European Euro for US Dollar EUR (€)	Sep. 30, 2011 Foreign Exchange Contracts To Sell European Euro for US Dollar USD ($)	Sep. 30, 2011 Foreign Exchange Contracts To Sell European Euro for US Dollar EUR (€)	Mar. 31, 2012 Foreign Exchange Contracts To Purchase British Pounds With US Dollars USD ($)	Mar. 31, 2012 Foreign Exchange Contracts To Purchase British Pounds With US Dollars GBP (£)	Sep. 30, 2011 Foreign Exchange Contracts To Purchase British Pounds With US Dollars USD ($)	Sep. 30, 2011 Foreign Exchange Contracts To Purchase British Pounds With US Dollars GBP (£)
Derivative [Line Items]
Contract amount of forward foreign currency contracts to sell foreign currency	$ 1,651	1,650	$ 7,663	8,000	$ 6,205	€ 4,650	$ 6,524	€ 4,830
Contract amount of forward foreign currency contracts to buy foreign currency									$ 5,100	£ 3,190	$ 6,100	£ 3,911