Quarterly Financial Data (Unaudited) - Summary of Unaudited Quarterly Results (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Quarterly Financial Information Disclosure [Abstract]
Total revenue	$ 15,336	$ 14,616	$ 13,604	$ 13,883	$ 14,297	$ 14,289	$ 13,695	$ 13,851	$ 57,439	$ 56,132	$ 51,928
Operating income from continuing operations	5,434	5,333	3,480	4,329	5,576	4,238	4,129	4,877	18,576	18,820	16,342
Income from continuing operations	2,444	3,674	2,459	3,630	3,733	3,178	3,420	4,248	12,207	14,579	10,129
Income (loss) from discontinued operations	(100)	(76)			(47)	(47)	682		(176)	588	102
Net income	$ 2,344	$ 3,598	$ 2,459	$ 3,630	$ 3,686	$ 3,131	$ 4,102	$ 4,248	$ 12,031	$ 15,167	$ 10,231
Basic income (loss) per share(1):
Continuing operations	$ 0.18	$ 0.27	$ 0.18	$ 0.26	$ 0.26	$ 0.22	$ 0.23	$ 0.29	$ 0.90	$ 1.01	$ 0.58
Discontinued operations	$ (0.01)	$ (0.01)	$ 0.00	$ 0.00	$ 0.00	$ 0.00	$ 0.05	$ 0.00	$ (0.01)	$ 0.04	$ 0.01
Net income	$ 0.17	$ 0.26	$ 0.18	$ 0.26	$ 0.26	$ 0.22	$ 0.28	$ 0.29	$ 0.88	$ 1.05	$ 0.59
Diluted income (loss) per share(1):
Continuing operations	$ 0.18	$ 0.27	$ 0.18	$ 0.26	$ 0.26	$ 0.22	$ 0.23	$ 0.29	$ 0.88	$ 0.99	$ 0.58
Discontinued operations	$ (0.01)	$ (0.01)	$ 0.00	$ 0.00	$ 0.00	$ 0.00	$ 0.05	$ 0.00	$ (0.01)	$ 0.04	$ 0.01
Net income	$ 0.17	$ 0.26	$ 0.18	$ 0.26	$ 0.26	$ 0.21	$ 0.28	$ 0.29	$ 0.87	$ 1.03	$ 0.59