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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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