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Business Segments - Operating Results for Two Business Segments (Detail) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017
Segment Reporting Information [Line Items] |  |  |  |
Revenues | $ 14,876 | $ 11,049 | $ 27,483 | $ 19,971
Operating profit/(loss) | 24,727 | (7,805) | 19,600 | (22,499)
Unallocated corporate expenses |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Operating profit/(loss) | (918) | (265) | (2,013) | (2,358)
Wind |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenues | 7,307 | 5,554 | 10,985 | 7,831
Wind | Operating Segments |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Operating profit/(loss) | 28,515 | (1,440) | 27,150 | (5,873)
Grid |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenues | 7,569 | 5,495 | 16,498 | 12,140
Grid | Operating Segments |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Operating profit/(loss) | $ (2,870) | $ (6,100) | $ (5,537) | $ (14,268)

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