CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE (LOSS) INCOME (unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ (251,086)	$ 107,175	$ 108,657	$ 27,731
Available-for-sale securities:
Unrealized holding losses, net of tax effect	(5,807)	(254)	(6,161)	(1,983)
Reclassification of realized transactions, net of tax effect	0	1,433	0	1,522
Defined benefit plans:
Actuarial gains (losses) related to defined benefit pension plans, net of tax benefit (provision) of $2,017, ($2,539), $3,402 and $1,206, respectively	1,212	6,998	(2,284)	(1,332)
Reclassification of realized transactions, net of tax effect	214	0	630	0
Change in net foreign currency translation adjustment	0	(3,109)	0	(5,678)
Other comprehensive (loss) income, net of tax effect	(4,381)	5,068	(7,815)	(7,471)
Comprehensive (loss) income	$ (255,467)	$ 112,243	$ 100,842	$ 20,260