Quarterly Results of Operations (UNAUDITED) (Results of Operations) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 209,008	$ 206,783	$ 201,424	$ 203,828	$ 173,000	$ 165,259	$ 157,489	$ 160,566	$ 821,043	$ 656,314	$ 641,443
Gross margin	75,491	82,188	80,546	80,350	66,849	61,929	60,199	60,508	$ 318,575	$ 249,485	$ 235,362
Income (loss) from continuing operations	$ 6,999	$ 25,532	$ 20,896	$ 27,032	$ 11,913	$ 16,065	$ 5,377	$ 14,928
Net income per share:
Basic income from continuing operations (in dollars per share)	$ 0.38	$ 1.40	$ 1.15	$ 1.50	$ 0.66	$ 0.89	$ 0.30	$ 0.83
Diluted income from continuing operations (in dollars per share)	$ 0.37	$ 1.37	$ 1.13	$ 1.47	$ 0.65	$ 0.88	$ 0.29	$ 0.82