Intangible Assets - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013	Mar. 31, 2012
Amortization Expense [Line Items]
Amortization expense	$ 0.2	$ 0.2	$ 0.4	$ 0.4