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, 2016 GBP (£)	Sep. 30, 2016 EUR (€)	Sep. 30, 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 | Short
Derivative [Line Items]
Contract amount of forward foreign currency contracts				CAD 2,750			$ 2,045
Fair value of forward foreign currency contracts to sell and buy foreign currency							0
Foreign Exchange Contracts To Sell European Euro for US Dollar | Short
Derivative [Line Items]
Contract amount of forward foreign currency contracts		€ 7,850	$ 8,743			€ 5,600	6,296
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	£ 7,721		10,000		£ 6,943		10,550
Fair value of forward foreign currency contracts to sell and buy foreign currency			$ 0				$ 0