Unaudited Supplementary Quarterly Financial Information - Unaudited Supplementary Quarterly Financial Information (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	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]
Total revenue	$ 27,424	$ 28,729	$ 29,222	$ 27,614	$ 26,781	$ 25,399	$ 27,900	$ 23,476	$ 112,989	$ 103,556	$ 100,881
Gross profit	9,957	10,416	10,886	10,107	10,734	9,657	10,041	7,140	41,366	37,572	35,279
Net (loss) income	$ 656	$ 976	$ 1,721	$ 711	$ 32,411	$ 1,772	$ 1,414	$ (889)	$ 4,064	$ 34,708	$ 1,447
Basic (loss) income per share	$ 0.06	$ 0.09	$ 0.15	$ 0.06	$ 2.99	$ 0.17	$ 0.13	$ (0.08)	$ 0.37	$ 3.21	$ 0.13
Diluted (loss) income per share	$ 0.05	$ 0.08	$ 0.13	$ 0.06	$ 2.55	$ 0.14	$ 0.12	$ (0.08)	$ 0.31	$ 2.88	$ 0.13