Derivative Instruments and Hedging Activities (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jul. 31, 2013		Jul. 31, 2012		Jul. 31, 2013		Jul. 31, 2012
Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net Gain (Loss) Recognized In Income Statement-Derivatives	$ (7,641)		$ 3,107		$ (9,489)		$ 7,205
Total Return Swap [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net Gain (Loss) Recognized In Income Statement-Derivatives	(7,641)		3,348		(9,247)		7,651
Total Return Swap [Member] | Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net Gain (Loss) Recognized In Income Statement-Derivatives	1,320	[1]	(225)	[1]	1,226	[1]	(370)	[1]
Interest rate caps and interest rate swaps [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net Gain (Loss) Recognized In Income Statement-Derivatives	$ 0		$ (241)		$ (242)		$ (446)

[1] The net gain (loss) recognized in interest expense from the change in fair value of the underlying TRS borrowings was $(1,320) and $(1,226) for the three and six months ended July 31, 2013, respectively, and $225 and $370 for the three and six months ended July 31, 2012, respectively, offsetting the gain (loss) recognized on the TRS (see Note F – Fair Value Measurements).