Short Term Investment - Additional Information (Detail) (USD $)	6 Months Ended	12 Months Ended
	Mar. 31, 2013 Investment	Sep. 30, 2012 Investment
Investment [Line Items]
Maturity Period of certificates of deposit	3 months	3 months
Maturity Period of certificates of deposit	1 year	1 year
Number of certificates of deposit limited to banking institution	1	1
Investments exceeding FDIC limit	$ 0	$ 0