Schedule II - Consolidated Valuation and Qualifying Accounts (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Allowance for Doubtful Accounts
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance At Beginning of Period	$ 292	$ 283	$ 235
Charged to Costs and Expenses	31	17	62
Charged to Other Accounts
Deductions		8	14
Balance at End of Period	323	292	283
Inventory Reserves
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance At Beginning of Period	3,116	2,694	2,611
Charged to Costs and Expenses	291	540	496
Charged to Other Accounts
Deductions	478	118	413
Balance at End of Period	2,929	3,116	2,694
Environmental Reserves
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance At Beginning of Period	12,684	13,535	14,293
Charged to Costs and Expenses	333	394	419
Charged to Other Accounts
Deductions	2,694	1,245	1,177
Balance at End of Period	10,323	12,684	13,535
Allowance For Tax Loss Valuation
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance At Beginning of Period	583	265	265
Charged to Costs and Expenses		318
Charged to Other Accounts
Deductions	318
Balance at End of Period	$ 265	$ 583	$ 265