Business Segments - Operating Results for Two Business Segments (Detail) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Revenues	$ 8,923	$ 13,345
Operating (loss) profit	(14,693)	(9,344)
Unallocated corporate expenses
Segment Reporting Information [Line Items]
Operating (loss) profit	(2,093)	(999)
Wind
Segment Reporting Information [Line Items]
Revenues	2,278	5,675
Wind | Operating Segments
Segment Reporting Information [Line Items]
Operating (loss) profit	(4,433)	(3,030)
Grid
Segment Reporting Information [Line Items]
Revenues	6,645	7,670
Grid | Operating Segments
Segment Reporting Information [Line Items]
Operating (loss) profit	$ (8,167)	$ (5,315)