Quarterly report pursuant to Section 13 or 15(d)

Intangible Assets - Summary of Intangible Assets (Detail)

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Intangible Assets - Summary of Intangible Assets (Detail) (USD $)
In Thousands, unless otherwise specified
Sep. 30, 2013
Mar. 31, 2013
Schedule Of Intangible Assets [Line Items]    
Finite-Lived Intangible Assets, Gross Carrying Amount $ 2,870 $ 2,870
Finite-Lived Intangible Assets, Accumulated Amortization 672 582
Finite-Lived Intangible Assets, Net Carrying Amount 2,198 2,288
Indefinite Lived Intangible Assets, Gross Carrying Amount 12,800 12,800
Indefinite Lived Intangible Assets, Net Carrying Amount 12,800 12,800
Backlog [Member]
   
Schedule Of Intangible Assets [Line Items]    
Finite-Lived Intangible Assets, Gross Carrying Amount 170 170
Finite-Lived Intangible Assets, Accumulated Amortization 170 170
Finite-Lived Intangible Assets, Net Carrying Amount      
Customer Relationships [Member]
   
Schedule Of Intangible Assets [Line Items]    
Finite-Lived Intangible Assets, Gross Carrying Amount 2,700 2,700
Finite-Lived Intangible Assets, Accumulated Amortization 502 412
Finite-Lived Intangible Assets, Net Carrying Amount 2,198 2,288
Permits [Member]
   
Schedule Of Intangible Assets [Line Items]    
Indefinite Lived Intangible Assets, Gross Carrying Amount 10,300 10,300
Indefinite Lived Intangible Assets, Net Carrying Amount 10,300 10,300
Tradename [Member]
   
Schedule Of Intangible Assets [Line Items]    
Indefinite Lived Intangible Assets, Gross Carrying Amount 2,500 2,500
Indefinite Lived Intangible Assets, Net Carrying Amount $ 2,500 $ 2,500