Summary Selected Quarterly Financial Data - Summary of Selected Consolidated Quarterly Financial Data (unaudited) (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 124,269	$ 108,596	$ 128,183	$ 100,649	$ 98,583	$ 84,890	$ 96,353	$ 77,749	$ 461,697	$ 357,575	$ 337,673
Income (loss) from operations	6,827	(1,640)	4,622	(10,884)	8,744	4,942	11,027	(2,288)	(1,075)	22,425	27,549
Net income (loss)	$ 4,890	$ (2,699)	$ 1,555	$ (13,316)	$ 5,375	$ 3,950	$ 7,788	$ (1,733)	$ (9,570)	$ 15,380	$ 15,140
Basic income (loss) per common share	$ 0.26	$ (0.15)	$ 0.08	$ (0.73)	$ 0.29	$ 0.22	$ 0.43	$ (0.10)	$ (0.52)	$ 0.85	$ 0.84
Diluted income (loss) per common share	$ 0.26	$ (0.15)	$ 0.08	$ (0.73)	$ 0.29	$ 0.21	$ 0.43	$ (0.10)	$ (0.52)	$ 0.84	$ 0.83