Notes Payable - Additional Information (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended				12 Months Ended			12 Months Ended				3 Months Ended		12 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2011	Apr. 30, 2011 4.00% Debentures due 2031	Jan. 31, 2013 4.00% Debentures due 2031 Convertible Subordinated Debt	Apr. 30, 2011 4.00% Debentures due 2031 Convertible Subordinated Debt	Jan. 31, 2012 6.25% Debentures due 2026, issued 2006	Jan. 31, 2012 6.25% Debentures due 2026, issued 2006 Convertible Subordinated Debt	Jan. 31, 2013 Term Loan due 2013	Jan. 31, 2012 Term Loan due 2013	Apr. 30, 2010 Term Loan due 2013	Jan. 31, 2013 Other Notes Payable	Nov. 30, 2009 Other Notes Payable	Jan. 31, 2013 Holder Optional Redemption Period 1 [Member] 4.00% Debentures due 2031 Convertible Subordinated Debt	Jan. 31, 2013 Holder Optional Redemption Period 2 [Member] 4.00% Debentures due 2031 Convertible Subordinated Debt	Jan. 31, 2013 Holder Optional Redemption Period 3 [Member] 4.00% Debentures due 2031 Convertible Subordinated Debt
Debt Instrument [Line Items]
Amortization End Date					2018-03
Issued Debt						$ 253,000					$ 20,000
Conversion price					$ 20.538
Total number of shares					12,319
Market price of common stock exceeding percent of the conversion price					120.00%
Market price of debentures declining to maximum percent of the value of the common stock					98.00%
Debentures Redemption Price	100.00%													100.00%	100.00%	100.00%
Debt effective interest rate					7.25%
Extinguishment of Debt, Amount								196,509		18,500
Loss on early extinguishment of debt before tax								11,192		312
Write-off of net unamortized debt discount								6,190
Premium on redemption	0	3,518	0					3,518
Write-off of unamortized debt issuance costs								$ 1,484
Term Loan Original Term									3 years
Interest rate				4.00%			6.25%						3.875%
Other Notes Payable, due date												Nov. 17, 2012