Other Significant Transactions (Details Textual 1) (USD $)	9 Months Ended		9 Months Ended			9 Months Ended
	Sep. 30, 2013 Property	Dec. 31, 2012	Sep. 30, 2013 Weighted Average [Member]	Sep. 30, 2013 West Harlem Property Loans [Member] Units Property	Dec. 31, 2012 West Harlem Property Loans [Member]	Sep. 30, 2013 West Harlem Property Loans [Member] Weighted Average [Member]	Dec. 31, 2006 Second Mortgage [Member] West Harlem Property Loans [Member]	Sep. 30, 2013 First Mortgage [Member] West Harlem Property Loans [Member]	Sep. 30, 2013 Legally Sold Portfolio, Not Derecognized for Accounting Purposes [Member]	Dec. 31, 2012 Legally Sold Portfolio, Not Derecognized for Accounting Purposes [Member]
Noncontrolling Interest [Line Items]
Number of Buildings Collateralizing Notes Receivable				84
Number apartment homes in buildings collateralizing notes receivable				1,596
Number Of Commercial Spaces In Buildings Collateralizing Notes Receivable				43
Recognized Investment In Loans And Purchase Option				$ 110,200,000	$ 110,500,000
Mortgage Loans on Real Estate, Face Amount of Mortgages							100,100,000	119,100,000
Notes Receivable Interest Rate Stated Percentage			4.30%			5.20%
Total cost of noncontrolling limited partnership interests acquired	10,700,000
Number Of Consolidated Partnerships In Which Remaining Noncontrolling Interests Acquired	1
Number of properties owned by consolidated partnerships in which remaining noncontrolling interests were acquired	2
Estimated Fair Value of Real Estate Corresponding to Noncontrolling Interests Acquired	21,000,000
Number of partnerships in legally sold portfolio	19
Number of consolidated properties in legally sold portfolio	16
Number of unconsolidated properties in legally sold portfolio	77
Noncontrolling interest in consolidated real estate partnerships	$ 245,735,000	$ 271,065,000							$ 51,900,000	$ 57,200,000