Quarterly Results of Operations (Unaudited) (Results of Operations) (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]
Net sales	$ 193,768	$ 221,842	$ 242,852	$ 239,798	$ 222,942	$ 226,863	$ 214,675	$ 214,611	$ 898,260	$ 879,091	$ 821,043
Gross margin	64,203	78,867	85,828	85,394	78,375	79,130	76,672	76,606	$ 314,292	$ 310,783	$ 318,575
Net income (loss)	$ (28,760)	$ 23,387	$ 24,293	$ 28,399	$ 24,452	$ 19,734	$ 17,329	$ 26,136
Net income (loss) per share:
Basic (in dollars per share)	$ (1.55)	$ 1.26	$ 1.31	$ 1.53	$ 1.33	$ 1.07	$ 0.94	$ 1.43
Diluted (in dollars per share)	$ (1.55)	$ 1.25	$ 1.30	$ 1.52	$ 1.31	$ 1.06	$ 0.93	$ 1.40