Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Sep. 30, 2019		Sep. 30, 2018		Sep. 30, 2019	Sep. 30, 2018
Revenues [Abstract]
Net sales	$ 327,397		$ 349,233		$ 672,639	$ 676,849
Operating costs and expenses:
Cost of sales	213,727		235,668		437,341	468,463
Selling, general and administrative expenses	49,327		52,258		97,212	100,800
Research and development	12,274		10,995		24,449	21,683
Restructuring charges	2,920		0		5,128	(96)
(Gain) loss on write down and disposal of long-lived assets	59		312		1,019	823
Total operating costs and expenses	278,307		299,233		565,149	591,673
Operating income (loss)	49,090		50,000		107,490	85,176
Non-operating (income) expense
Interest income	(812)		(375)		(1,621)	(753)
Interest expense	2,751		7,287		5,296	14,323
Gain (Loss) Related to Litigation Settlement	63,098		4,320		63,098	4,282
Other (income) expense, net	(1,915)		(309)		(2,641)	(11,642)
Income (loss) before income taxes and equity income (loss) from equity method investments	(14,032)		39,077		43,358	78,966
Income tax expense (benefit)	1,700		2,000		18,500	6,600
Income (loss) before equity income (loss) from equity method investments	(15,732)		37,077		24,858	72,366
Equity income (loss) from equity method investments	472		64		222	(5)
Net income (loss)	$ (15,260)	[1]	$ 37,141	[1]	$ 25,080	$ 72,361
Net income (loss) per basic share:
Net income (loss) per basic share (in usd per share)	$ (0.26)		$ 0.64		$ 0.43	$ 1.26
Net income (loss) per diluted share (in usd per share)	(0.26)		0.63		0.42	1.22
Dividends declared per share	$ 0.05		$ 0.00		$ 0.10	$ 0.00
Weighted-average shares outstanding:
Basic (in shares)	58,528		57,799		58,440	57,570
Diluted (in shares)	58,528		59,197		59,175	59,119

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