Derivative Financial Instruments - Summary of Outstanding Forward Foreign Currency Contracts by Currency (Detail) € in Thousands, £ in Thousands, CAD in Thousands, $ in Thousands	Mar. 31, 2016 CAD	Mar. 31, 2016 GBP (£)	Mar. 31, 2016 EUR (€)	Mar. 31, 2016 USD ($)	Sep. 30, 2015 CAD	Sep. 30, 2015 GBP (£)	Sep. 30, 2015 EUR (€)	Sep. 30, 2015 USD ($)
Foreign Exchange Contracts to Sell Canadian Dollar for US Dollar
Derivative [Line Items]
Fair value of forward foreign currency contracts to sell and buy foreign currency				$ 0				$ 0
Foreign Exchange Contracts to Sell Canadian Dollar for US Dollar | Foreign currency forward contracts | Short | Not Designated as Hedging Instrument
Derivative [Line Items]
Contract amount of forward foreign currency contracts	CAD 1,250			963	CAD 2,750			2,045
Foreign Exchange Contracts To Sell European Euro for US Dollar
Derivative [Line Items]
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 | Foreign currency forward contracts | Short | Not Designated as Hedging Instrument
Derivative [Line Items]
Contract amount of forward foreign currency contracts			€ 5,500	6,303			€ 5,600	6,296
Foreign Exchange Contracts To Purchase British Pounds With US Dollars
Derivative [Line Items]
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 | Foreign currency forward contracts | Short | Not Designated as Hedging Instrument
Derivative [Line Items]
Contract amount of forward foreign currency contracts		£ 5,026		$ 7,250		£ 6,943		$ 10,550