Segment Reporting Footnote Tagging (Details)	6 Months Ended				6 Months Ended						6 Months Ended
	Jun. 30, 2012 Integer segments properties	Jun. 30, 2012 Tax-exempt mortgage revenue bonds [Member] Unit	Jun. 30, 2012 MF Properties [Member] Unit entities	Jun. 30, 2012 Consolidated VIEs [Member] Integer Unit	Jun. 30, 2012 Unconsolidated Available for Sale Securities [Member] Integer	Jun. 30, 2012 Consolidated VIEs [Member] Integer	Jun. 30, 2012 Consolidated Properties Subject to Sale [Member] properties	Oct. 31, 2011 Consolidated Properties Subject to Sale [Member] properties	Jun. 30, 2010 Consolidated Properties Subject to Sale [Member] properties	Jun. 30, 2012 Consolidated Properties Subject to Sale [Member] MF Properties [Member] entities Unit	Jun. 30, 2012 Consolidated Properties Subject to Sale [Member] Unconsolidated Available for Sale Securities [Member] Integer	Jun. 30, 2012 Consolidated Properties [Member] properties	Jun. 30, 2010 Consolidated Properties [Member] properties	Jun. 30, 2012 Consolidated Properties [Member] MF Properties [Member] entities
Segment Reporting Information [Line Items]
Number of Reportable Segments	3
Number of Available for Sale Securities	19				16	3					2
Number of Units in Real Estate Property		3,712	1,410	650						362
Number of Real Estate Properties			12				3	3	3	3		9	4	9
Number of Variable Interest Entities	5			3