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, 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 segment revenues	$ 80,975	$ 74,753	$ 82,811	$ 75,187	$ 80,681	$ 75,363	$ 82,947	$ 73,071	$ 313,726	$ 312,062	$ 297,650
Income from operations	4,108	5,341	10,093	(715)	6,188	4,925	7,080	20	18,827	18,213	21,833
Net income	$ 2,020	$ 4,450	$ 5,750	$ (224)	$ 3,599	$ 3,043	$ 4,289	$ (66)	$ 11,996	$ 10,865	$ 13,024
Basic income (loss) per common share	$ 0.11	$ 0.25	$ 0.32	$ (0.01)	$ 0.20	$ 0.17	$ 0.23		$ 0.67	$ 0.58	$ 0.62
Diluted income (loss) per common share	$ 0.11	$ 0.25	$ 0.31	$ (0.01)	$ 0.19	$ 0.16	$ 0.23		$ 0.66	$ 0.57	$ 0.61