Accounting for the Impairment or Disposal of Long-Lived Assets - Asset Impairments in Reportable Segments (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Asset Impairment Charges	$ 117,000	$ 1,904,000	$ 6,851,000
Tangible Asset Impairment Charges [Abstract]
Land Impairment		200,000
Impairment Losses Related to Real Estate Partnerships		800,000	4,600,000
Impairment of Real Estate	100,000	900,000	2,300,000
Carolinas [Member]
Segment Reporting Information [Line Items]
Asset Impairment Charges	0	0	36,000
Chicago Milwaukee [Member]
Segment Reporting Information [Line Items]
Asset Impairment Charges	0	0	514,000
Richmond Hampton Roads [Member]
Segment Reporting Information [Line Items]
Asset Impairment Charges	0	0	27,000
South Florida [Member]
Segment Reporting Information [Line Items]
Asset Impairment Charges	0	0	(51,000)	[1]
Southeastern PA [Member]
Segment Reporting Information [Line Items]
Asset Impairment Charges	106,000		1,699,000
Tampa [Member]
Segment Reporting Information [Line Items]
Asset Impairment Charges	0	248,000	0
United Kingdom [Member]
Segment Reporting Information [Line Items]
Asset Impairment Charges	0	784,000	4,597,000
Other Segments [Member]
Segment Reporting Information [Line Items]
Asset Impairment Charges	$ 11,000	$ 872,000	$ 29,000

[1] Represents recovery of estimated sales costs on properties sold.