Derivative Financial Instruments - Summary of Outstanding Forward Foreign Currency Contracts by Currency (Detail) - Foreign currency forward contracts - Not Designated as Hedging Instrument € in Thousands, £ in Thousands, CAD in Thousands, $ in Thousands	Sep. 30, 2015 CAD	Sep. 30, 2015 GBP (£)	Sep. 30, 2015 EUR (€)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 CAD	Sep. 30, 2014 GBP (£)	Sep. 30, 2014 EUR (€)	Sep. 30, 2014 USD ($)
Foreign Exchange Contracts to Sell Canadian Dollar for US Dollar | Short
Derivative [Line Items]
Contract amount of forward foreign currency contracts	CAD 2,750			$ 2,045	CAD 3,300			$ 2,960
Fair value of forward foreign currency contracts to sell and buy foreign currency				0				0
Foreign Exchange Contracts To Sell European Euro for US Dollar | Short
Derivative [Line Items]
Contract amount of forward foreign currency contracts			€ 5,600	6,296			€ 3,800	4,790
Fair value of forward foreign currency contracts to sell and buy foreign currency				0				0
Foreign Exchange Contracts To Purchase British Pounds With US Dollars | Long
Derivative [Line Items]
Contract amount of forward foreign currency contracts		£ 6,943		10,550		£ 6,795		11,000
Fair value of forward foreign currency contracts to sell and buy foreign currency				$ 0				$ 0