Selected Quarterly Financial Data (Unaudited) - Schedule of Selected Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	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]
Total revenues	$ 22,632	$ 17,985	$ 17,376	$ 16,958	$ 16,077	$ 15,884	$ 14,065	$ 12,871	$ 74,951	$ 58,897	$ 48,796
Income (loss) before provision for income taxes	5,003	727	2,266	2,038	630	1,967	(10,325)	(362)	10,034	(8,143)	(272)
Provision for income taxes	0	0	0	0	0	0	17	36	0	0	123
Net income (loss)	$ 5,003	$ 727	$ 2,266	$ 2,038	$ 630	$ 1,967	$ (10,342)	$ (398)	$ 10,034	$ (8,143)	$ (395)
Earnings (loss) per common share, basic (in usd per share)	$ 0.10	$ 0.02	$ 0.07	$ 0.06	$ 0.03	$ 0.09	$ (0.47)	$ (0.02)	$ 0.26	$ (0.36)	$ (0.02)
Earnings (loss) per common share, diluted (in usd per share)	$ 0.10	$ 0.02	$ 0.07	$ 0.06	$ 0.03	$ 0.09	$ (0.47)	$ (0.02)	$ 0.26	$ (0.36)	$ (0.02)
Weighted-average number of common shares outstanding, basic (in shares)	47,660	39,125	31,278	31,257	24,419	22,255	22,231	22,228	37,380	22,788	22,228
Weighted-average number of common shares outstanding, diluted (in shares)	47,660	39,125	31,278	31,257	24,586	22,436	22,231	22,228	37,380	22,788	22,228