CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Unrealized gains (losses) on available-for-sale securities, tax	$ 61	$ (239)	$ 0
Change in loss on derivative contract, tax	823	77	0
Change in supplemental executive retirement plan pension liability, tax	(927)	1,264	0
Change in Pension Plan minimum liability, tax	215	1,093	0
Change in Other Benefit Plan minimum liability, tax	$ (2,046)	$ 5,081	$ (769)