Derivative Instruments and Hedging Activities (Details Textual) (USD $)	3 Months Ended		9 Months Ended
	Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2013	Oct. 31, 2012
Derivative [Line Items]
Notional amount	$ 640,000,000		$ 640,000,000
Loss on cash flow hedges to be reclassified within next twelve months			25,355,000
SIFMA rate	0.08%		0.08%
Net gain (loss) from change in fair value of underlying TRS borrowings recognized in interest expense	(1,864,000)	148,000	(3,090,000)	518,000
Adjustment for nonperformance risk	8,190,000		8,190,000
Aggregate fair value of derivative instruments in a liability position	139,816,000		139,816,000
Posted collateral consisting of cash and notes receivable	105,736,000		105,736,000
Forward starting swaps and Treasury options [Member]
Derivative [Line Items]
Notional amount	0		0
Minimum [Member] | Interest rate swap agreements [Member]
Derivative [Line Items]
Derivative, term of ontract			1 year
Minimum [Member] | Caps and floors [Member]
Derivative [Line Items]
Derivative, term of ontract			1 year
Minimum [Member] | Treasury options [Member]
Derivative [Line Items]
Derivative, term of ontract			5 years
Maximum [Member] | Interest rate swap agreements [Member]
Derivative [Line Items]
Derivative, term of ontract			10 years
Maximum [Member] | Caps and floors [Member]
Derivative [Line Items]
Derivative, term of ontract			3 years
Maximum [Member] | Treasury options [Member]
Derivative [Line Items]
Derivative, term of ontract			10 years
Designated as Hedging Instrument [Member] | Total Return Swap [Member]
Derivative [Line Items]
Notional amount	275,685,000		275,685,000
Cash Flow Hedging [Member]
Derivative [Line Items]
Loss on interest rate cash flow hedge ineffectiveness	$ 2,366,000		$ 2,963,000