Notes Payable Notes Payable - Recognized Amounts in Interest Expense in the Consolidated Statement of Operations Related to the 6.25% Debentures (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jan. 31, 2014	Jan. 31, 2013	Jan. 31, 2012
Debt Instrument
Interest expense at the contractual interest rate	$ 19,452	$ 18,866	$ 31,444
6.25% Debentures due 2026, issued 2006
Debt Instrument
Interest expense at the contractual interest rate	0	0	2,900
Amortization of debt discount	$ 0	$ 0	$ 793