Quarterly Financial Data (Details) - 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
Revenue, Net	$ 90,387	$ 86,016	$ 83,781	$ 81,484	$ 79,896	$ 77,457	$ 78,677	$ 73,230
Gross Profit	48,257	46,265	43,761	42,514	39,685	38,147	37,542	36,027	$ 180,797	$ 151,401	$ 154,732
Net Income	$ 5,463	$ 16,266	$ 13,570	$ 9,686	$ 7,372	$ 6,428	$ 5,878	$ 6,657	$ 44,985	$ 26,335	$ 40,418
Basic	$ 0.34	$ 1.02	$ 0.86	$ 0.62	$ 0.48	$ 0.42	$ 0.39	$ 0.44	$ 2.84	$ 1.72	$ 2.75
Diluted	$ 0.33	$ 0.98	$ 0.83	$ 0.60	$ 0.46	$ 0.42	$ 0.38	$ 0.43	$ 2.73	$ 1.68	$ 2.65