Derivative Instruments and Hedging Activities (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Apr. 30, 2013		Apr. 30, 2012
Not Designated as Hedging Instrument [Member]
Impact of gains and losses related to derivative instruments
Net Gain (Loss) Recognized Derivatives	$ (1,848)		$ 4,098
Total Return Swap [Member] | Not Designated as Hedging Instrument [Member]
Impact of gains and losses related to derivative instruments
Net Gain (Loss) Recognized Derivatives	(1,606)		4,303
Total Return Swap [Member] | Fair Value Hedging [Member]
Impact of gains and losses related to derivative instruments
Net Gain (Loss) Recognized Derivatives	(94)	[1]	(145)	[1]
Interest rate caps and interest rate swaps [Member] | Not Designated as Hedging Instrument [Member]
Impact of gains and losses related to derivative instruments
Net Gain (Loss) Recognized Derivatives	$ (242)		$ (205)

[1] The net gain (loss) recognized in interest expense from the change in fair value of the underlying TRS borrowings was $94 and $145 for the three months ended April 30, 2013 and 2012, respectively, offsetting the gain (loss) recognized on the TRS (see Note F – Fair Value Measurements).