Summary of Significant Accounting Policies (Details Textual) (USD $)	12 Months Ended																			12 Months Ended
	Jan. 31, 2012 Segment State Entity	Jan. 31, 2011 Entity	Jan. 31, 2010	Jan. 31, 2010 Retained Earnings	Jan. 31, 2009 Prior Period Adjustment [Member] Retained Earnings	Jan. 31, 2012 Maximum [Member]	Jan. 31, 2012 Minimum [Member]	Jan. 31, 2012 Nonrecourse Mortgage Debt [Member]	Jan. 31, 2011 Nonrecourse Mortgage Debt [Member]	Jan. 31, 2010 Nonrecourse Mortgage Debt [Member]	Jan. 31, 2012 The Nets [Member] Y	Jan. 31, 2011 The Nets [Member]	Jan. 31, 2010 The Nets [Member]	Jan. 31, 2012 Commercial Group [Member]	Jan. 31, 2011 Commercial Group [Member] Entity	Jan. 31, 2012 Residential Group [Member]	Jan. 31, 2011 Residential Group [Member] Entity	Jan. 31, 2012 Land Development Group [Member]	Jan. 31, 2011 Land Development Group [Member]	Jan. 31, 2010 Gladden Farms II [Member]	Jan. 31, 2012 Primary Beneficiary [Member] Entity	Jan. 31, 2012 Primary Beneficiary [Member] Commercial Group [Member] Entity	Jan. 31, 2012 Primary Beneficiary [Member] Residential Group [Member] Entity	Jan. 31, 2012 Primary Beneficiary [Member] Land Development Group [Member] Entity	Jan. 31, 2012 Variable Interest Entity, Not Primary Beneficiary [Member] Entity
Variable Interest Entity [Line Items]
Increase in Noncontrolling interest due to consolidation of the VIE																				$ 5,010,000
Increase in real estate due to consolidation of the VIE																				21,643,000
Variable Interest Entities																					33	13	18	2	60
Properties representing Variable Interest Entities																					22	11	9	2
Increase in gain recorded as interest and other income due to consolidation of VIE																				1,774,000
Number of Entity Consolidated															1
Number of Entity Deconsolidated		9													2		7
Cumulative effect of adoption of new accounting guidance for the consolidation of VIE's		74,034,000
Schedule of Equity Method Investments [Line Items]
Estimated useful lives finite-lived intangible asset											5
Portion of amortization expense recorded by Nets attributed to the intangible assets											2,130,000	1,228,000	14,517,000
Debt Instrument [Line Items]
Interest Rate								5.50%	5.50%	5.50%
Interest Rate								6.40%	6.40%	6.40%
Debt instrument basis spread on variable rate								0.90%	0.90%	0.90%
Maturity date of Swap Agreement								Sep. 01, 2017	Sep. 01, 2017	Sep. 01, 2017
Property, Plant and Equipment [Line Items]
Lease terms of tenants in retail centre and office building						30 years	1 year
Error Correction and Prior Period revision [Line Items]
Allowance for projects under development revision			10,888,000	10,888,000	10,888,000
Significant Accounting Policies (Textual) [Abstract]
Number of Strategic Business Units	3
Number of reportable segment	5
Total Assets	10,504,283,000	12,059,701,000												7,970,069,000	8,617,287,000	2,022,135,000	2,825,527,000	352,248,000	498,190,000
Number of States in which Entity has Consolidated Assets	28
Estimated useful lives of buildings and certain first generation tenant allowances	50 years
Replacement reserves previously written off reinstated by HUD			10,226,000
Reclassified from investments in and advances to unconsolidated entities to cash distributions and losses in excess of investments in unconsolidated entities on the consolidated balance sheet	279,708,000	290,492,000
Book overdrafts included in account payable and accrued expenses	0	10,371,000
Unrealized losses on an interest rate swap associated with office building	143,303,000	102,387,000	89,637,000
Total rate of return swap contract amount	640,000,000	640,000,000	640,000,000
All in Lender Interest Rate on Mortgage	interest rate of 6.40% (5.50% swap rate plus 0.90% lender spread)	interest rate of 6.40% (5.50% swap rate plus 0.90% lender spread)	interest rate of 6.40% (5.50% swap rate plus 0.90% lender spread)
Expected amount to be reclassified from accumulated OCI to interest expense within the next twelve months	33,345,000
Maximum period of investment arrangement	7 years
Minimum Compliance Regulation on tax credit	0 years
Maximum Compliance Regulation on tax credit	7 years
Income related to the sale of tax credits	27,296,000	31,979,000	32,698,000
Maximum loss exposure for unconsolidated variable interest entities	65,000,000
Collateralized borrowings of variable interest entities	29,000,000
Decrease in real estate due to deconsolidation of the VIE	744,999,000
Decrease in Cash and equivalents due to deconsolidation of the VIE	4,588,000
Decrease in restricted cash and escrowed funds due to deconsolidation of the VIE	66,882,000
Decrease in other assets due to deconsolidation of the VIE	18,561,000
Decrease in nonrecourse mortgage debt due to deconsolidation of the VIE	670,000,000
Decrease in accounts payable, accrued expenses and other liabilities due to deconsolidated of the VIE	35,009,000
Increase in investments and advances to unconsolidated entities due to deconsolidated of the VIE	$ 130,021,000