Derivative Financial Instruments - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Mar. 31, 2013
Derivative Financial Instruments [Line Items]
Foreign currency hedge arrangements	Mar. 31, 2013
Accrued unrealized foreign exchange losses	$ 0.2
Foreign Currency Forward Contracts
Derivative Financial Instruments [Line Items]
Foreign currency forward contract to hedge	20.0
Canadian Subsidiary
Derivative Financial Instruments [Line Items]
Denominated intercompany accounts payable	$ 34.4