Summarized Consolidated Quarterly Information - Summarized Consolidated and Condensed Quarterly Financial Information (Detail) - USD ($)	3 Months Ended								12 Months Ended
	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, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Subscription revenue	$ 14,206,000	$ 12,137,000	$ 13,416,000	$ 11,131,000	$ 10,726,000	$ 10,469,000	$ 10,194,000	$ 9,946,000	$ 50,890,438	$ 41,335,155	$ 34,721,088
Income from continuing operations	2,342,000	1,508,000	2,928,000	1,293,000	1,524,000	1,130,000	915,000	1,047,000	8,070,983	4,616,385	17,933,431
Net income	$ 3,372,000	$ 1,644,000	$ 4,067,000	$ 1,222,000	$ 1,476,000	$ 1,080,000	$ 822,000	$ 669,000	$ 10,304,983	$ 4,047,122	$ 17,596,942
Per share amounts - basic:
Income from continuing operations	$ 0.21	$ 0.13	$ 0.26	$ 0.12	$ 0.14	$ 0.10	$ 0.08	$ 0.10	$ 0.72	$ 0.42	$ 1.65
Net income	0.30	0.15	0.36	0.11	0.13	0.10	0.07	0.06	0.92	0.37	1.62
Per share amounts - diluted:
Income from continuing operations	0.20	0.13	0.25	0.11	0.12	0.10	0.08	0.09	0.69	0.39	1.57
Net income	$ 0.29	$ 0.14	$ 0.35	$ 0.10	$ 0.11	$ 0.09	$ 0.07	$ 0.06	$ 0.88	$ 0.34	$ 1.54
Weighted average number of common shares outstanding:
Basic	11,251,000	11,236,000	11,229,000	11,191,000	11,145,000	11,119,000	11,102,000	10,979,000	11,226,932	11,086,690	10,884,533
Diluted	11,744,000	11,721,000	11,690,000	11,693,000	11,688,000	11,653,000	11,531,000	11,463,000	11,706,495	11,593,079	11,396,559