Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015	Apr. 01, 2017
Deferred tax assets	$ 407	$ 96
Valuation allowance	315,092	301,393
Increase in valuation allowance	13,700
Deferred tax asset reflecting the benefit of deductions from the exercise of stock options	13,000
Undistributed earnings available for repatriation	2,100
Reversal of uncertain tax positions	0	$ 0	$ 1,100
Austria
Net operating loss carryforwards	37,100
China
Net operating loss carryforwards	$ 17,900
Net operating loss carryforward period	5 years
Statute of limitations for audit, period	3 years
Federal
Net operating loss carryforwards	$ 798,000
Research and development and other tax credit carryforwards	9,500
State
Net operating loss carryforwards	143,000
Research and development and other tax credit carryforwards	3,200
Foreign earnings repatriated
Federal and state deferred tax liability	700
Power Quality Systems, Inc.
Net operating loss carryforwards	$ 3,700
Accounting Standards Update 2016-09
Deferred tax assets				$ 18,000
Valuation allowance				$ 18,000