Business Segments - Additional Information (Detail) $ in Thousands	12 Months Ended
Mar. 31, 2018 USD ($) segment MW	Mar. 31, 2017 USD ($) segment	Mar. 31, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of reportable business segments \| segment	2	2
Stock-based compensation expense	$ 2,692	$ 2,892	$ 3,248
Restructuring and impairment charges	1,527	0	779
Change in fair value of contingent consideration	$ 71	$ 0	$ 0
Geographic concentration risk \| Sales revenue, net \| Outside The United States
Segment Reporting Information [Line Items]
Risk percentage	64.00%	78.00%	85.00%
Customer concentration risk \| Sales revenue, net \| Inox Wind Limited
Segment Reporting Information [Line Items]
Risk percentage	27.00%	59.00%	62.00%
Unallocated corporate expenses
Segment Reporting Information [Line Items]
Stock-based compensation expense	$ 2,700	$ 2,900	$ 3,200
Minimum
Segment Reporting Information [Line Items]
Megawatts of drive trains and power ratings \| MW	2

Other than Temporary Impairment Losses, Investments and Restructuring Credits

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Power of wind turbines.

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Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

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