Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Revenues [Abstract]
Net sales	[1]	$ 350,175	$ 306,576	$ 1,027,024	$ 882,090
Operating costs and expenses:
Cost of sales	[1]	226,425	214,288	694,888	630,781
Selling, general and administrative expenses		48,271	47,751	149,071	125,799
Research and development		11,357	9,907	33,040	28,690
Restructuring charges		1,718	3,530	1,622	6,536
(Gain) loss on write down and disposal of long-lived assets		788	(902)	1,611	(922)
Total operating costs and expenses	[1]	288,559	274,574	880,232	790,884
Operating income (loss)	[1]	61,616	32,002	146,792	91,206
Non-operating (income) expense:
Interest income		(572)	(252)	(1,325)	(413)
Interest expense		4,480	7,407	18,803	25,732
Acquisition (gain) loss		0	(310)	0	(137,183)
Other (income) expense, net		14,006	4,769	6,646	21,061
Income (loss) before income taxes and equity income (loss) from equity method investments	[1]	43,702	20,388	122,668	182,009
Income tax expense (benefit)	[1]	2,600	2,037	9,200	6,041
Income (loss) before equity income (loss) from equity method investments	[1]	41,102	18,351	113,468	175,968
Equity income (loss) from equity method investments		(296)	238	(301)	75,879
Net income (loss)	[1],[2]	$ 40,806	$ 18,589	$ 113,167	$ 251,847
Net income (loss) per basic share:
Net income (loss) per basic share (in usd per share)		$ 0.70	$ 0.33	$ 1.96	$ 4.91
Net income (loss) per diluted share (in usd per share)		0.69	0.32	1.91	4.31
Dividends declared per share		$ 0.05	$ 0.00	$ 0.05	$ 0.00
Weighted-average shares outstanding:
Basic (in shares)		58,010	56,778	57,717	51,340
Diluted (in shares)		59,111	58,937	59,116	58,431

[1] Three and nine months ended December 31, 2017 adjusted due to the adoption of ASC 606.

[2] Three and nine months ended December 31, 2017 adjusted due to the adoption of ASC 606.