Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	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, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Data (Unaudited)
Net revenues	$ 39,407	$ 33,116	$ 35,031	$ 30,971	$ 36,236	$ 31,465	$ 32,618	$ 29,471	$ 33,202	$ 28,781	$ 29,055	$ 20,951	$ 138,525	$ 129,790	$ 111,989
Operating (loss) income	12,603	9,579	10,677	7,164	11,079	7,951	8,780	7,056	10,211	5,559	6,612	3,647	40,023	34,867	26,027
Net income	$ 5,922	$ 4,349	$ 5,029	$ 2,700	$ 4,934	$ 2,910	$ 3,431	$ 2,462	$ 4,330	$ 663	$ 5,318	$ 248	$ 18,000	$ 13,739	$ 10,557
Earnings per share:
Basic (in dollars per share)	$ 0.15	$ 0.11	$ 0.12	$ 0.06	$ 0.11	$ 0.07	$ 0.08	$ 0.06	$ 0.10	$ 0.02	$ 0.13	$ 0.01	$ 0.43	$ 0.32	$ 0.25
Dilutive (in dollars per share)	$ 0.15	$ 0.11	$ 0.12	$ 0.06	$ 0.11	$ 0.07	$ 0.08	$ 0.06	$ 0.10	$ 0.02	$ 0.13	$ 0.01	$ 0.43	$ 0.31	$ 0.25