Segment Reporting (Schedule Of Selected Results Of Operations And Asset Information) (Details) - USD ($)		3 Months Ended				6 Months Ended
		Jun. 30, 2016		Jun. 30, 2015		Jun. 30, 2016		Jun. 30, 2015		Dec. 31, 2015
Segment Reporting Information [Line Items]
Total revenues		$ 149,227,000		$ 148,567,000		$ 302,150,000		$ 302,282,000
Total operating and interest expenses	[1]	101,186,000		105,331,000		209,479,000		218,184,000
Equity in earnings (loss) of unconsolidated joint ventures		(614,000)		(2,329,000)		(2,168,000)		(5,858,000)
Net operating income (loss)	[2]	47,427,000		40,907,000		90,503,000		78,240,000
Total assets		4,213,540,000				4,213,540,000				$ 4,053,963,000
Total long-lived assets	[3]	3,577,911,000				3,577,911,000				3,466,427,000
Total investments in unconsolidated joint ventures		315,200,000				315,200,000				303,457,000
Corporate & Other, Including Eliminations [Member]
Segment Reporting Information [Line Items]
Total revenues	[4]	(3,181,000)		(1,157,000)		(4,924,000)		(2,015,000)
Total operating and interest expenses	[1],[4]	21,473,000		27,250,000		44,521,000		54,929,000
Net operating income (loss)	[2],[4]	(24,654,000)		(28,407,000)		(49,445,000)		(56,944,000)
Total assets	[4]	62,801,000				62,801,000				41,535,000
Total long-lived assets	[3],[4]	(3,571,000)				(3,571,000)				(1,531,000)
Real Estate - Commercial And Other [Member]
Segment Reporting Information [Line Items]
Total revenues		133,768,000		134,613,000		270,721,000		274,217,000
Total operating and interest expenses	[1]	64,368,000		64,158,000		133,378,000		136,008,000
Equity in earnings (loss) of unconsolidated joint ventures		1,405,000		798,000		1,082,000		(570,000)
Net operating income (loss)	[2]	70,805,000		71,253,000		138,425,000		137,639,000
Total assets		3,165,791,000				3,165,791,000				3,166,577,000
Total long-lived assets	[3]	2,898,185,000				2,898,185,000				2,886,583,000
Total investments in unconsolidated joint ventures		78,185,000				78,185,000				76,140,000
Real Estate - Multi Family [Member]
Segment Reporting Information [Line Items]
Total revenues		9,219,000		6,842,000		18,205,000		13,579,000
Total operating and interest expenses	[1]	5,920,000		4,872,000		11,335,000		8,541,000
Equity in earnings (loss) of unconsolidated joint ventures		(2,100,000)		(3,336,000)		(3,331,000)		(5,497,000)
Net operating income (loss)	[2]	1,199,000		(1,366,000)		3,539,000		(459,000)
Total assets		972,292,000				972,292,000				836,020,000
Total long-lived assets	[3]	679,374,000				679,374,000				577,705,000
Total investments in unconsolidated joint ventures		236,383,000				236,383,000				225,850,000
Multi Family Services [Member]
Segment Reporting Information [Line Items]
Total revenues		9,421,000	[5]	8,269,000	[6]	18,148,000	[5]	16,501,000	[6]
Total operating and interest expenses	[1]	9,425,000	[7]	9,051,000	[8]	20,245,000	[7]	18,706,000	[8]
Equity in earnings (loss) of unconsolidated joint ventures		81,000		209,000		81,000		209,000
Net operating income (loss)	[2]	77,000		(573,000)		(2,016,000)		(1,996,000)
Total assets		12,656,000				12,656,000				9,831,000
Total long-lived assets	[3]	3,923,000				3,923,000				3,670,000
Total investments in unconsolidated joint ventures		632,000				632,000				$ 1,467,000
Fee revenue		3,600,000		1,600,000		6,300,000		2,800,000
Management fee and salary reimbursement expenses		$ 1,700,000		$ 954,000		$ 3,100,000		$ 1,900,000

[1] Total operating and interest expenses represent the sum of: real estate taxes; utilities; operating services; direct construction costs; real estate services expenses; general and administrative and interest expense (net of interest income). All interest expense, net of interest and other investment income, (including for property-level mortgages) is excluded from segment amounts and classified in Corporate & Other for all periods.

[2] Net operating income represents total revenues less total operating and interest expenses (as defined in Note "a"), plus equity in earnings (loss) of unconsolidated joint ventures, for the period.

[3] Long-lived assets are comprised of net investment in rental property, unbilled rents receivable and goodwill.

[4] Corporate & Other represents all corporate-level items (including interest and other investment income, interest expense, non-property general and administrative expense, construction services revenue and direct construction costs) as well as intercompany eliminations necessary to reconcile to consolidated Company totals.

[5] Includes $3.6 million and $6.3 million of fees and salary reimbursements earned for the three and six months ended June 30, 2016, respectively, from the multi-family real estate segment, which are eliminated in consolidation.

[6] Includes $1.6 million and $2.8 million of fees and salary reimbursements earned for the three and six months ended June 30, 2015, respectively, from the multi-family real estate segment, which are eliminated in consolidation.

[7] Includes $1.7 million and $3.1 million of management fees and salary reimbursement expenses for the three and six months ended June 30, 2016, respectively, from the multi-family real estate segment, which are eliminated in consolidation.

[8] Includes $954,000 and $1.9 million of management fees and salary reimbursement expenses for the three and six months ended June 30, 2015, respectively, from the multi-family real estate segment, which are eliminated in consolidation.