Business Segments - Additional Information (Detail) $ in Thousands	12 Months Ended
Mar. 31, 2017 USD ($) segment MW	Mar. 31, 2016 USD ($)	Mar. 31, 2015 USD ($)
Segment Reporting Information [Line Items]
Number of reportable business segments \| segment	2
Stock-based compensation expense	$ 2,892	$ 3,248	$ 5,936
Restructuring and impairments	0	779	5,366
Impairment of minority interest investments	$ 0	$ 746	$ 3,464
Customer concentration risk \| Sales revenue, net \| Inox Wind Limited
Segment Reporting Information [Line Items]
Risk percentage	59.00%	62.00%	56.00%
Geographic concentration risk \| Sales revenue, net \| Outside The United States
Segment Reporting Information [Line Items]
Risk percentage	78.00%	85.00%	86.00%
Minimum
Segment Reporting Information [Line Items]
Megawatts of drive trains and power ratings \| MW	2
Unallocated corporate expenses
Segment Reporting Information [Line Items]
Stock-based compensation expense	$ 2,892	$ 3,248	$ 5,936

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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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