Schedule of Accrued Expenses (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Mar. 31, 2013
Accounts Payable and Accrued Liabilities, Current [Abstract]
Payroll and Incentive Compensation	$ 11,145	$ 11,827
Benefits	9,662	10,349
Interest	4,813	4,813
Property Taxes	4,967	3,235
Power and Fuel	2,539	3,146
Sales and Use Tax	1,129	591
Acquisition Related Expenses		2,023
Other	6,530	5,365
Accrued expenses, total	$ 40,785	$ 41,349