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, 2013	Jan. 31, 2012	Jan. 31, 2011
Debt Instrument [Line Items]
Interest Expense	$ 18,866	$ 31,444	$ 18,411
6.25% Debentures due 2026, issued 2006
Debt Instrument [Line Items]
Interest Expense	0	2,900	10,322
Amortization of Debt Discount (Premium)	$ 0	$ 793	$ 3,010