CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Net sales	$ 191,157	$ 242,852	$ 389,967	$ 482,650
Cost of sales	121,188	157,024	254,368	311,428
Gross margin	69,969	85,828	135,599	171,222
Selling, General and Administrative Expense	41,694	43,649	82,024	86,901
Research and Development Expense	7,295	7,843	15,100	15,452
Restructuring and impairment charges	0	1,083	0	1,905
Other operating (income) expense, net	(112)	40	(92)	951
Operating income	21,092	33,213	38,567	66,013
Equity income in unconsolidated joint ventures	1,022	1,742	2,240	2,579
Pension settlement charges	(55)	0	(55)	0
Other (expense) income, net	634	(1,401)	(152)	3
Interest expense, net	(1,779)	(2,038)	(2,986)	(3,976)
Income before income tax expense	20,914	31,516	37,614	64,619
Income tax expense	6,394	7,223	9,835	11,927
Net income	$ 14,520	$ 24,293	$ 27,779	$ 52,692
Basic earnings per share (in dollars per share)	$ 0.78	$ 1.31	$ 1.49	$ 2.84
Diluted earnings per share (in dollars per share)	$ 0.78	$ 1.30	$ 1.49	$ 2.82
Shares used in computing:
Basic earnings per share (in shares)	18,676	18,568	18,673	18,562
Diluted earnings per share (in shares)	18,681	18,730	18,686	18,711