Quarterly Information (Unaudited) - Schedule of Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 9,670	$ 9,105	$ 8,522	$ 7,404	$ 7,866	$ 6,440	$ 5,672	$ 5,389	$ 5,544	$ 4,660	$ 4,484	$ 4,463	$ 34,701	$ 25,367	$ 19,150
Cost of revenue	940	793	720	942	825	591	558	497	520	608	450	571
Operating expenses	7,889	7,618	7,171	6,804	6,079	5,539	4,628	4,758	5,089	5,702	6,246	5,373
Operating income (loss)	841	694	631	(342)	962	310	486	134	(65)	(1,650)	(2,212)	(1,481)	1,824	1,892	(5,408)
Other income (expense), net	23	45	30	36	25	30	21	15	67	17	19	13	134	91	118
Income tax benefit (provision)	96		(79)	(16)	(32)	578		(3)					1	543	(2)
Net income (loss)	$ 960	$ 739	$ 582	$ (322)	$ 955	$ 918	$ 507	$ 146	$ 2	$ (1,633)	$ (2,193)	$ (1,468)	$ 1,959	$ 2,526	$ (5,292)
Net income (loss) per share:
Basic income (loss) per share	$ 0.03	$ 0.02	$ 0.02	$ (0.01)	$ 0.03	$ 0.03	$ 0.02	$ 0.00	$ 0.00	$ (0.05)	$ (0.07)	$ (0.05)	$ 0.06	$ 0.08	$ (0.17)
Shares used in calculating net income (loss) per share - basic	32,086,223	31,823,386	31,325,577	31,094,417	30,969,157	30,764,694	30,697,391	30,618,097	30,510,587	30,481,168	30,453,455	30,402,397	31,586,535	30,790,258	30,466,063
Diluted income (loss) per share	$ 0.03	$ 0.02	$ 0.02	$ (0.01)	$ 0.03	$ 0.03	$ 0.02	$ 0.00	$ 0.00	$ (0.05)	$ (0.07)	$ (0.05)	$ 0.06	$ 0.08	$ (0.17)
Shares used in calculating net income (loss) per share - diluted	34,859,861	34,531,964	33,133,920	31,094,417	31,664,178	31,645,696	31,321,259	31,173,815	31,022,148	30,481,168	30,453,455	30,402,397	33,818,501	31,480,241	30,466,063