Carrying Amounts and Estimated Fair Values of Company Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Mar. 31, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivatives assets, Fair Value	$ 241	[1]	$ 812	[1]
Derivatives liabilities, Fair Value	3,738	[1]	4,753	[1]
Derivatives assets, Carrying Amount	241	[1]	812	[1]
Derivatives liabilities, Carrying Amount	3,738	[1]	4,753	[1]
Convertible Notes Payable
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible Notes, Fair Value	155,273	[2]	148,272	[2]
Convertible Notes, Carrying Amount	$ 217,350	[3]	$ 200,100	[3]

[1] Represents interest rate swap agreements, lead and foreign currency hedges (see Note 12 for asset and liability positions of the interest rate swap agreements, lead and foreign currency hedges at March 31, 2013 and March 31, 2012).

[2] The fair value amounts of the Convertible Notes represent the trading values of the Convertible Notes with a principal value of $172,500 at March 31, 2013 and March 31, 2012.

[3] The carrying amounts of the Convertible Notes at March 31, 2013 and March 31, 2012 represent the $172,500 principal value, less the unamortized debt discount (see Note 8).