Derivative Instruments and Hedging Activities (Details 1) (Cash Flow Hedging [Member], USD $)	3 Months Ended
	Apr. 30, 2013	Apr. 30, 2012
Derivative instruments gain loss in financial statements
Gain (Loss) Recognized in OCI (Effective Portion)	$ (312,000)	$ 8,725,000
Gain (loss) reclassified from Accumulated OCI, Effective Amount	(1,001,000)	(1,055,000)
Gain (loss) reclassified from Accumulated OCI, Ineffective Amount	2,000	2,000
Interest rate caps, interest rate swaps and Treasury options [Member]
Derivative instruments gain loss in financial statements
Gain (Loss) Recognized in OCI (Effective Portion)	(312,000)	8,725,000
Interest rate caps, interest rate swaps and Treasury options [Member] | Interest expense [Member]
Derivative instruments gain loss in financial statements
Gain (loss) reclassified from Accumulated OCI, Effective Amount	(954,000)	(967,000)
Gain (loss) reclassified from Accumulated OCI, Ineffective Amount	0	0
Interest rate caps, interest rate swaps and Treasury options [Member] | Equity in earnings (loss) of unconsolidated entities [Member]
Derivative instruments gain loss in financial statements
Gain (loss) reclassified from Accumulated OCI, Effective Amount	(47,000)
Gain (loss) reclassified from Accumulated OCI, Ineffective Amount	2,000
Interest rate caps, swaps and Treasury options [Member]
Derivative instruments gain loss in financial statements
Gain (Loss) Recognized in OCI (Effective Portion)	0
Interest rate caps and Treasury options [Member]
Derivative instruments gain loss in financial statements
Gain (Loss) Recognized in OCI (Effective Portion)		0
Interest rate caps and Treasury options [Member] | Equity in earnings (loss) of unconsolidated entities [Member]
Derivative instruments gain loss in financial statements
Gain (loss) reclassified from Accumulated OCI, Effective Amount		(88,000)
Gain (loss) reclassified from Accumulated OCI, Ineffective Amount		$ 2,000