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Business Segments - Operating Results for Two Business Segments (Detail) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2017 | Dec. 31, 2016 | Sep. 30, 2016 | Jun. 30, 2016 | Mar. 31, 2016 | Dec. 31, 2015 | Sep. 30, 2015 | Jun. 30, 2015 | Mar. 31, 2017 | Mar. 31, 2016 | Mar. 31, 2015
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revenues | $ 16,195 | $ 27,148 | $ 18,507 | $ 13,345 | $ 27,524 | $ 25,772 | $ 19,004 | $ 23,723 | $ 75,195 | $ 96,023 | $ 70,530
Operating loss | $ (6,988) | $ (4,060) | $ (7,150) | $ (9,344) | $ (1,708) | $ (3,312) | $ (6,841) | $ (8,257) | (27,542) | (20,118) | (52,517)
Unallocated corporate expenses |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Operating loss |  |  |  |  |  |  |  |  | (2,892) | (4,027) | (11,306)
Wind |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revenues |  |  |  |  |  |  |  |  | 47,269 | 68,883 | 51,307
Wind | Operating Segments |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Operating loss |  |  |  |  |  |  |  |  | (4,174) | (1,256) | (14,321)
Grid |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revenues |  |  |  |  |  |  |  |  | 27,926 | 27,140 | 19,223
Grid | Operating Segments |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Operating loss |  |  |  |  |  |  |  |  | $ (20,476) | $ (14,835) | $ (26,890)

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