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]
Revenues	$ 227,511	$ 217,405	$ 228,080	$ 237,182	$ 214,198	$ 194,099	$ 184,471	$ 188,163	$ 910,178	$ 780,931	$ 731,725
Gross Profit	95,668	89,720	94,855	102,571	98,371	92,626	78,590	83,500	382,814	353,087	338,711
Net income (loss)	$ 27,396	$ 23,917	$ 21,390	$ 31,643	$ 26,981	$ 23,587	$ 12,713	$ 17,073	$ 104,346	$ 80,354	$ (342,750)
Basic (in dollars per share)	$ 1.61	$ 1.38	$ 1.20	$ 1.76	$ 1.49	$ 1.31	$ 0.70	$ 0.93	$ 5.95	$ 4.43	$ (18.96)
Diluted (in dollars per share)	$ 1.59	$ 1.36	$ 1.18	$ 1.73	$ 1.47	$ 1.29	$ 0.69	$ 0.92	$ 5.85	$ 4.37	$ (18.96)
Impairment of goodwill and intangible assets									$ 0	$ 0	$ 531,634