Fair Value Of Financial Instruments (Narrative) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended			9 Months Ended
	Oct. 31, 2012	Jan. 31, 2013	Jan. 15, 2013 Derivative	Jan. 31, 2013 Interest Rate Derivatives [Member]	Jan. 31, 2013 Second Lien Notes [Member]	Jan. 31, 2013 Senior Subordinated Notes Due 2019 Notes [Member]	Jan. 31, 2013 Convertible Bonds [Member]
Fair Value And Carrying Value By Balance Sheet Grouping [Line Items]
Fair value of fixed rate debt including the senior subordinated notes and the Series 2005R-2 converted bonds		$ 342,349
Carrying value of fixed rate debt including the senior subordinated notes and the Series 2005R-2 converted bonds		344,608
Revolver, carrying value		141,700
Fixed rate debt, due date					Jul. 15, 2014	Feb. 15, 2019	Jan. 01, 2025
Number of forward starting interest rate derivatives			2
Total notional amount of interest rate derivatives				150,000
Interest payable rate				1.40%
Second Lien Notes callable date					Jan. 15, 2013
Interest rate derivative maturity date				Mar. 15, 2016
Forward starting interest rate derivative agreements	75,000
Other loss (income)	$ 3,626