Derivative Instruments and Hedging Activities (Details 1) (Cash Flow Hedging [Member], USD $) In Thousands	3 Months Ended	6 Months Ended
Jul. 31, 2011	Jul. 31, 2010	Jul. 31, 2011	Jul. 31, 2010
Derivative Instruments Activity in Financial Statements
Gain (Loss) Recognized in OCI (Effective Portion)	$ (20,850)	$ (40,966)	$ (22,889)	$ (40,114)
Gain (loss) reclassified from Accumulated OCI	(1,038)	(717)	(1,817)	(1,486)
Ineffectiveness Recognized in Interest Expense on Derivatives	(555)	3	(555)	(1)
Interest rate caps and treasury options [Member] \| Equity in loss of unconsolidated entities [Member]
Derivative Instruments Activity in Financial Statements
Gain (loss) reclassified from Accumulated OCI	(94)		(182)
Ineffectiveness Recognized in Interest Expense on Derivatives	(555)		(555)
Interest rate caps, interest rate swaps and Treasury options [Member] \| Interest expense [Member]
Derivative Instruments Activity in Financial Statements
Gain (loss) reclassified from Accumulated OCI	(944)	(697)	(1,635)	(1,448)
Ineffectiveness Recognized in Interest Expense on Derivatives		3		1
Interest rate caps, interest rate swaps and Treasury options [Member]
Derivative Instruments Activity in Financial Statements
Gain (Loss) Recognized in OCI (Effective Portion)	(20,850)	(40,966)	(22,889)	(40,114)
Treasury options [Member] \| Equity in loss of unconsolidated entities [Member]
Derivative Instruments Activity in Financial Statements
Gain (loss) reclassified from Accumulated OCI		(20)		(38)
Ineffectiveness Recognized in Interest Expense on Derivatives				$ (2)

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The income statement location of the effective portion of net gain or loss reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 205G

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 44C
-Subparagraph b
-Clause 3

+ Details

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- Definition

The portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments representing (a) the amount of the hedge ineffectiveness and (b) the amount, if any, excluded from the assessment of hedge effectiveness.

+ References

+ Details

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- Definition

The effective portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period.

+ References

+ Details

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