Summarized Consolidated Quarterly Information - Summarized Consolidated and Condensed Quarterly Financial Information (Detail) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Subscription revenue	$ 10,726,000	$ 10,469,000	$ 10,194,000	$ 9,946,000	$ 9,209,000	$ 8,780,000	$ 8,498,000	$ 8,234,000	$ 41,335,155	$ 34,721,088	$ 31,228,644
Income from continuing operations	1,524,000	1,130,000	915,000	1,047,000	16,304,000	705,000	522,000	402,000	4,616,385	17,933,431	8,013,330
Net income	$ 1,476,000	$ 1,080,000	$ 822,000	$ 669,000	$ 16,214,000	$ 649,000	$ 484,000	$ 250,000	$ 4,047,122	$ 17,596,942	$ (4,283,582)
Per share amounts - basic:
Income from continuing operations	$ 0.14	$ 0.10	$ 0.08	$ 0.10	$ 1.49	$ 0.06	$ 0.05	$ 0.04	$ 0.42	$ 1.65	$ 0.75
Net income	$ 0.13	$ 0.10	$ 0.07	$ 0.06	$ 1.49	$ 0.06	$ 0.04	$ 0.02	$ 0.37	$ 1.62	$ (0.40)
Per share amounts - diluted:
Income from continuing operations	$ 0.12	$ 0.10	$ 0.08	$ 0.09	$ 1.42	$ 0.05	$ 0.05	$ 0.04	$ 0.39	$ 1.57	$ 0.73
Net income	$ 0.11	$ 0.09	$ 0.07	$ 0.06	$ 1.41	$ 0.05	$ 0.04	$ 0.02	$ 0.34	$ 1.54	$ (0.39)
Weighted average number of common shares outstanding:
Basic	11,145,000	11,119,000	11,102,000	10,979,000	10,909,000	10,908,000	10,892,000	10,828,000	11,086,690	10,884,533	10,685,333
Diluted	11,688,000	11,653,000	11,531,000	11,463,000	11,464,000	11,445,000	11,398,000	11,348,000	11,593,079	11,396,559	11,034,082