Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Net sales	$ 1,260,554	$ 1,382,818	$ 1,200,181
Operating costs and expenses:
Cost of sales	840,066	924,276	860,744
Selling, general and administrative expenses	194,766	202,642	173,620
Research and development	49,264	44,612	39,114
Restructuring charges	8,882	8,779	14,843
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down	19,710	1,660	(992)
Net (gain) loss on sales and disposals of assets	800	(1,000)	(1,200)
Total operating costs and expenses	1,112,688	1,181,969	1,087,329
Operating income	147,866	200,849	112,852
Non-operating (income) expense:
Interest income	3,325	2,035	809
Interest expense	11,021	21,239	32,882
Business combination bargain purchase, gain recognized	0	0	130,880
Gain (Loss) Related to Litigation Settlement	64,695	6,701	9,900
Other (income) expense, net	(4,356)	4,513	14,692
Income before income taxes and equity income (loss) from equity method investments	79,831	170,431	187,067
Income tax expense (benefit)	38,526	(39,460)	9,132
Income before equity income (loss) from equity method investments	41,305	209,891	177,935
Equity income (loss) from equity method investments	76	(3,304)	76,192
Net income	$ 41,381	$ 206,587	$ 254,127
Net income (loss) per basic share:
Net income (loss) (in dollars per share)	$ 0.71	$ 3.57	$ 4.81
Net income (loss) per diluted share:
Net income (loss) (in dollars per share)	$ 0.70	$ 3.50	$ 4.33
Weighted-average shares outstanding:
Basic (in shares)	58,574	57,840	52,798
Diluted (in shares)	59,415	59,082	58,640