Stockholders' Equity - Summary of Stock Option Activity (Detail) (USD $)	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Summary of stock options outstanding and changes
Number of Shares, Outstanding Beginning Balance	8,142,468
Number of Shares, Granted	2,151,507
Number of Shares, Exercised	(1,033,833)	(1,673,811)
Number of Shares, Forfeited	(437,101)
Number of Shares, Outstanding Ending Balance	8,823,041	8,142,468
Number of Shares, Vested and expected to vest in the future	8,566,637
Options Exercisable, Number of Shares	4,621,266
Weighted Average Exercise Price, Beginning Balance	$ 2.67
Weighted Average Exercise Price per Share, Granted	$ 2.89
Weighted Average Exercise Price per Share, Exercised	$ 1.45
Weighted Average Exercise Price per Share, Forfeited	$ 3.08
Weighted Average Exercise Price, Ending Balance	$ 2.85	$ 2.67
Weighted Average Exercise Price per Share, Vested and expected to vest in the future	$ 2.85
Options Exercisable, Weighted Average Exercise Price	$ 2.83
Options Outstanding, Weighted Average Remaining Contractual Term	7 years 4 months 24 days
Weighted Average Remaining Contractual Term, Vested and expected to vest in the future	7 years 3 months 18 days
Weighted Average Remaining Contractual Term, Exercisable	6 years 3 months 18 days
Aggregate Intrinsic Value, Outstanding	$ 14,106,009
Aggregate Intrinsic Value, Vested and expected to vest in the future	13,748,940
Aggregate Intrinsic Value, Exercisable	$ 8,232,487