Selected Quarterly Financial Data (unaudited) (Quarterly Financial Information) (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
Selected Quarterly Financial Data (unaudited) [Abstract]
Revenue	$ 170,632	$ 190,061	$ 187,103	$ 165,876	$ 145,844	$ 139,239	$ 117,324	$ 98,596	$ 713,672	$ 501,003	$ 301,563
Gross profit	128,068	142,933	140,710	125,147	109,091	107,201	88,799	74,808	536,858	379,899	227,812
Income from continuing operations before income taxes	18,981	20,583	27,778	25,021	20,170	17,828	17,619	14,931	92,363	70,548	40,326
Net income	$ 19,881	$ 15,902	$ 21,383	$ 20,750	$ 15,653	$ 13,781	$ 14,133	$ 12,222	$ 77,916	$ 55,789	$ 27,721
Earnings per share - basic	$ 1.71	$ 1.36	$ 1.80	$ 1.75	$ 1.32	$ 1.15	$ 1.17	$ 1.02	$ 6.62	$ 4.67	$ 2.32
Earnings per share - diluted	$ 1.66	$ 1.32	$ 1.75	$ 1.70	$ 1.30	$ 1.14	$ 1.16	$ 1.01	$ 6.43	$ 4.62	$ 2.29