Accounting for the Impairment or Disposal of Long-Lived Assets Asset Impairment (Details) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Property, Plant and Equipment [Line Items]
Impairment - real estate assets	$ 0	$ 15,739,000
Carolinas Richmond [Member]
Property, Plant and Equipment [Line Items]
Impairment - real estate assets		13,400,000
Southeastern PA [Member]
Property, Plant and Equipment [Line Items]
Impairment - real estate assets		$ 2,300,000