Business Segments - Total Business Segments Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Mar. 31, 2015
Segment Reporting Asset Reconciling Item [Line Items]
Total assets	$ 142,915	$ 133,825
Operating Segments | Wind
Segment Reporting Asset Reconciling Item [Line Items]
Total assets	35,227	41,947
Operating Segments | Grid
Segment Reporting Asset Reconciling Item [Line Items]
Total assets	40,440	42,482
Corporate assets
Segment Reporting Asset Reconciling Item [Line Items]
Total assets	$ 67,248	$ 49,396