Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (73,324)	$ 79,812	$ 33,291
Other comprehensive income (loss):
Cumulative translation adjustments	(3,229)	4,889	(1,000)
Recognition of actuarial net (loss) gain from pension and other post-retirement plans, net of (benefit) taxes of ($976), $435, and ($368)	(2,278)	1,353	(858)
Changes in market value of investments:
Changes in unrealized gains (losses), net of taxes (benefit) of $19, $15, and $0	60	(6)	(59)
Total net change in market value of investments	60	(6)	(59)
Changes in market value of derivatives:
Changes in market value of derivatives, net of tax (benefits) of ($172), $267, and ($167)	(524)	812	(277)
Reclassification adjustment for net (losses) gains included in net income (loss), net of (benefit) taxes of $138, ($219), and $135	437	(681)	223
Total net change in market value of derivatives	(87)	131	(54)
Other comprehensive income (loss)	(5,534)	6,367	(1,971)
Total comprehensive income (loss)	$ (78,858)	$ 86,179	$ 31,320