Acquisitions And Development (Narrative) (Details) (USD $)	0 Months Ended		12 Months Ended							3 Months Ended		3 Months Ended	12 Months Ended			3 Months Ended
	Jan. 28, 2011	Sep. 22, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2010 1200 East West [Member]	Dec. 31, 2007 1200 East West [Member]	Dec. 31, 2008 Courts At Huntington Station [Member]	Dec. 31, 2010 Courts At Huntington Station Phase One [Member]	Dec. 31, 2011 Courts At Huntington Station Phase Two [Member]	Mar. 31, 2011 The Apartments At Cobblestone Square [Member]	Dec. 31, 2011 The Apartments At Cobblestone Square [Member]	Dec. 31, 2011 Eleven 55 Ripley [Member]	Dec. 31, 2011 Arbor Park [Member]	Dec. 31, 2011 Falkland Chase [Member]	Dec. 31, 2011 Falkland North [Member]	Dec. 31, 2011 Courts At Spring Mill Station [Member]	Dec. 31, 2011 Other Assets [Member]
Acquisitions And Development [Line Items]
Closing costs related to acquired apartment communities			$ 3,219,000	$ 2,871,000
Revenues from acquired apartment communities			49,763,000	12,831,000
Net income attributable to common shareholders from acquired apartment communities			9,098,000	2,018,000
Construction in progress for development, number of buildings										8		2
Construction in progress for development, number of units										314		379
Number of buildings completed							4	2
Community acquired, number of units			41,951			247	421	202	219		51
Construction in progress, gross			64,201,000	119,992,000	82,976,000			83,640,000	121,931,000		25,596,000	25,476,000				13,129,000
Number of garden apartments under redevelopment phase													851
Number of buildings under redevelopment phase													52
Renovation period, in years													4
Number of buildings under renovation													5
Number of unit under renovation													52
Pre-redevelopment construction, number of units														450	182	385
Number of buildings completed and occupied													11
Number of units completed					247								128
Number of units occupied													103
Pre-redevelopment included in other assets															4,591,000
Purchase of non-performing mortgage notes		1,433,000
Collection of mortgage loans	1,015,000
Purchase of remaining non-performing mortgage notes			418,000
Note receivable																	429,000
Average cost per apartment unit					$ 329,000				$ 289,000
Square feet of retail space						10,600