Stock-Based Compensation - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserve for issuance	417,406		417,406
Options granted and outstanding to purchase	3,816,751		3,816,751		3,419,285	1,910,794	729,096
Number of Options Outstanding, Granted			780,000		1,509,166	1,229,500
Options granted outside of Equity Incentive plans			165,000
Stock-based compensation expense			$ 1,719,582	$ 750,782
Fair value of the options granted	7,085,656	103,293
Intrinsic value of the options exercised			3,115,175	0
Dividend yield			0.00%	0.00%
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense			570,707	0
Number of restricted stock units issued under 2013 incentive plan	470,000		470,000
Arrowhead
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Pre-tax compensation expense	$ 17,294,117		$ 17,294,117
Weighted average period to recognize pre-tax compensation expense	3 years 6 months
2000 Stock Option Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserve for issuance	50,750		50,750
Options granted and outstanding to purchase	50,750		50,750
2004 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserve for issuance	2,735,597		2,735,597
Options granted and outstanding to purchase	2,733,595		2,733,595
Number of Options Outstanding, Granted			0
2013 Incentive plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserve for issuance	4,000,000		4,000,000
Options granted and outstanding to purchase	615,000		615,000
Number of Options Outstanding, Granted			615,000