Business Segments - Additional Information (Detail) $ in Thousands	3 Months Ended	12 Months Ended
Jun. 30, 2018 USD ($) segment MW	Jun. 30, 2017 USD ($)	Mar. 31, 2018 segment
Segment Reporting Information [Line Items]
Number of reportable business segments \| segment	2		2,000
Stock-based compensation expense	$ 785	$ 754
Restructuring	310	1,339
Unallocated corporate expenses
Segment Reporting Information [Line Items]
Stock-based compensation expense	800	800
Restructuring	$ 300	$ 1,300
Minimum
Segment Reporting Information [Line Items]
Megawatts of drive trains and power ratings \| MW	2

Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

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