SELECTED QUARTERLY FINANCIAL DATA (Unaudited) (Details) - 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 revenue	$ 130,419	$ 129,309	$ 143,218	$ 120,631	$ 111,422	$ 110,494	$ 110,815	$ 104,806	$ 523,577	$ 437,537	$ 421,053
Total operating costs and expenses	101,397	107,858	109,372	90,324	76,725	80,843	79,391	79,929	408,951	316,888	297,330
Income from operations	29,022	21,451	33,846	30,307	34,697	29,651	31,424	24,877	114,626	120,649	123,723
Total other expense, net	11,237	10,650	10,521	7,038	6,721	5,364	5,068	5,699	39,446	22,852	22,615
Income before provision for income taxes	17,785	10,801	23,325	23,269	27,976	24,287	26,356	19,178	75,180	97,797	101,108
Provision for income taxes	4,430	3,802	6,145	5,673	5,846	7,913	6,056	6,544	20,050	26,359	38,861
Net income	$ 13,355	$ 6,999	$ 17,180	$ 17,596	$ 22,130	$ 16,374	$ 20,300	$ 12,634	$ 55,130	$ 71,438	$ 62,247
Net income per share
Basic (in dollars per share)	$ 0.40	$ 0.19	$ 0.42	$ 0.46	$ 0.60	$ 0.44	$ 0.55	$ 0.34	$ 1.46	$ 1.95	$ 1.64
Diluted (in dollars per share)	$ 0.40	$ 0.18	$ 0.42	$ 0.46	$ 0.57	$ 0.42	$ 0.53	$ 0.33	$ 1.46	$ 1.87	$ 1.56