Business Segments - Operating Results for Two Business Segments (Detail) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Segment Reporting Information [Line Items]
Revenues	$ 13,345	$ 23,723
Operating (loss) profit	(9,344)	(8,257)
Unallocated corporate expenses
Segment Reporting Information [Line Items]
Operating (loss) profit	(999)	(1,876)
Wind | Operating Segments
Segment Reporting Information [Line Items]
Revenues	5,675	18,164
Operating (loss) profit	(3,030)	127
Grid | Operating Segments
Segment Reporting Information [Line Items]
Revenues	7,670	5,559
Operating (loss) profit	$ (5,315)	$ (6,508)