Business Segments - Total Business Segments Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Asset Reconciling Item [Line Items]
Total assets	$ 88,175	$ 100,244
Operating Segments | Wind
Segment Reporting Asset Reconciling Item [Line Items]
Total assets	16,790	18,346
Operating Segments | Grid
Segment Reporting Asset Reconciling Item [Line Items]
Total assets	37,012	31,060
Corporate assets
Segment Reporting Asset Reconciling Item [Line Items]
Total assets	$ 34,373	$ 50,838