Derivative Instruments and Hedging Activities (Details Textual) (USD $)	12 Months Ended
	Jan. 31, 2012 Derivatives	Jan. 31, 2011	Jan. 31, 2010
Derivative Instruments and Hedging Activities (Textual) [Abstract]
Gain (Loss) on forward swaps not designated as hedges included in interest expense	$ (229,000)	$ 1,200,000	$ (4,761,000)
Number of missed forecasted transactions	0	0	1
Total ineffectiveness recognized as missed forecasted transaction			928,000
Gain loss on cash flow hedges to be reclassified within next twelve months	27,718,000
SIFMA rate	0.08%
Aggregate notional amount of TRS designated as fair value hedging instruments	270,757,000
Duration of forward swap rate	five to ten years
Number of forward swaps outstanding	0
Aggregate notional amount of forward swaps terminated	62,800,000	107,000,000
Net loss recognized on change in underlying TRS borrowings recognized in interest expense	11,855,000	1,924,000	16,351,000
Adjustment for nonperformance risk	16,127,000
Aggregate fair value of derivative instruments in a liability position	190,147,000
Posted collateral consisting of cash and notes receivable	82,180,000
Ineffectiveness of cash flow hedge included in interest expenses			1,012,000
Caps and Floors [Member]
Derivative [Line Items]
Derivative Instrument Duration of agreement	one to three years
Treasury options [Member]
Derivative [Line Items]
Derivative Instrument Duration of agreement	five to ten years
Treasury options outstanding	$ 0
Interest rate swap agreements [Member]
Derivative [Line Items]
Derivative Instrument Duration of agreement	one to ten years