Segment Information (Tables)

3 Months Ended

Mar. 31, 2013

Segment Reporting, Asset Reconciling Item [Line Items]

Reconciliation of Assets from Segment to Consolidated [Table Text Block]

		March 31, 2013		December 31, 2012
Total assets
	Northeast - Southeastern PA	$	810,493	$	816,437
	Northeast - Lehigh / Central PA	777,171		780,182
	Northeast - Other	385,243		388,446
	Central	1,092,854		1,073,631
	South	1,451,573		1,455,805
	Metro	459,515		478,835
	United Kingdom	121,262		138,025
	Other	48,562		42,818
Total assets		$	5,146,673	$	5,174,179

Company's Reportable Segments [Table Text Block]

REGIONS	MARKETS
Northeast	Southeastern PA; Lehigh/Central PA; New Jersey; Maryland
Central	Minnesota; Chicago/Milwaukee; Houston; Arizona
South	Richmond/Hampton Roads; Carolinas; Jacksonville; Orlando; South Florida; Tampa
Metro	Philadelphia; Metro Washington, D.C.
United Kingdom	County of Kent; West Midlands; Cambridge

Schedule of Segment Reporting Information, by Segment, Revenue and Net Operating Income [Table Text Block]

The operating information by reportable segment is as follows (in thousands):

		For the Three Months Ended
		March 31,
		2013			2012
Operating revenue
	Northeast - Southeastern PA	$	41,054		$	42,195
	Northeast - Lehigh / Central PA	24,677			24,077
	Northeast - Other	15,394			17,400
	Central	32,401			32,144
	South	53,562			54,012
	Metro	9,763			8,188
	United Kingdom	1,100			1,162
Segment-level operating revenue		177,951			179,178
Reconciliation to total operating revenue
	Discontinued operations	(1,634		)	(12,404		)
	Other	256			168
Total operating revenue		$	176,573		$	166,942
Net operating income
	Northeast - Southeastern PA	$	22,613		$	25,170
	Northeast - Lehigh / Central PA	16,668			16,195
	Northeast - Other	8,322			9,105
	Central	18,923			17,747
	South	33,317			32,654
	Metro	6,796			5,629
	United Kingdom	(133		)	(229		)
Segment-level net operating income		106,506			106,271
Reconciliation to income from continuing operations
	Interest expense (1)	(32,082		)	(30,904		)
	Depreciation/amortization expense (2)	(29,307		)	(25,652		)
	Gain on property dispositions	1,800			523
	Equity in earnings of unconsolidated joint ventures	1,757			916
	General and administrative expense (2)	(13,877		)	(11,550		)
	Discontinued operations excluding gain on property dispositions	(880		)	(4,323		)
	Income taxes (2)	(491		)	(86		)
	Other	(1,363		)	(980		)
Income from continuing operations		$	32,063		$	34,215

(1) Includes interest on discontinued operations.

(2) Excludes costs which are included in determining segment-level net operating income.