Annual report pursuant to Section 13 and 15(d)

Intangible Assets - Summary of Intangible Assets (Detail)

v3.7.0.1
Intangible Assets - Summary of Intangible Assets (Detail) - USD ($)
$ in Thousands
Mar. 31, 2017
Mar. 31, 2016
Schedule Of Intangible Assets [Line Items]    
Indefinite Lived Intangible Assets, Gross Carrying Amount $ 12,800 $ 12,800
Indefinite Lived Intangible Assets, Net Carrying Amount 12,800 12,800
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
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 1,132 952
Finite-Lived Intangible Assets, Net Carrying Amount $ 1,568 $ 1,748