Derivative Instruments and Hedging Activities (Details Textual) (USD $)	3 Months Ended		9 Months Ended
	Oct. 31, 2011 Derivatives	Oct. 31, 2010	Oct. 31, 2011 Derivatives	Oct. 31, 2010	Jan. 31, 2011	May 03, 2010
Derivative Instruments and Hedging Activities (Textual)
Gain loss on cash flow hedges to be reclassified within next twelve months			$ 27,834,000
SIFMA rate	0.14%		0.14%
Aggregate notional amount of TRS designated as fair value hedging instruments	260,982,000		260,982,000
Duration of forward swap rate			five to ten years
Number of forward swaps outstanding	0		0
Aggregate notional amount of forward swap terminated					62,800,000	107,000,000
Gain (Loss) on forward swaps not designated as hedges included in interest expense		(1,409,000)	229,000	(6,134,000)
Net loss recognized on change in underlying TRS borrowings recognized in interest expense	2,190,000	2,620,000	9,654,000	8,492,000
Adjustment for nonperformance risk	15,951,000		15,951,000
Aggregate fair value of derivative instruments in a liability position	181,939,000		181,939,000
Posted collateral consisting of cash and notes receivable	74,678,000		74,678,000
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		$ 0
Interest rate swap agreements [Member]
Derivative [Line Items]
Derivative Instrument Duration of agreement			one to ten years