Business Segments - Total Business Segments Assets (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Mar. 31, 2014
Segment Reporting Asset Reconciling Item [Line Items]
Total assets	$ 155,847	$ 168,509
Operating Segments | Wind
Segment Reporting Asset Reconciling Item [Line Items]
Total assets	47,569	36,701
Operating Segments | Grid
Segment Reporting Asset Reconciling Item [Line Items]
Total assets	44,779	54,342
Corporate assets
Segment Reporting Asset Reconciling Item [Line Items]
Total assets	$ 63,499	$ 77,466