Business Segments - Total Business Segments Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Mar. 31, 2017
Segment Reporting Asset Reconciling Item [Line Items]
Total assets	$ 104,603	$ 100,244
Operating Segments | Wind
Segment Reporting Asset Reconciling Item [Line Items]
Total assets	17,162	18,346
Operating Segments | Grid
Segment Reporting Asset Reconciling Item [Line Items]
Total assets	26,811	31,060
Corporate assets
Segment Reporting Asset Reconciling Item [Line Items]
Total assets	$ 60,630	$ 50,838