Discontinued Operations and Assets Held for Sale (Table Illustration of Number of Properties in Discontinued Operations) (Details)	3 Months Ended		6 Months Ended	12 Months Ended
	Jun. 30, 2014 buildings	Mar. 31, 2014 buildings	Jun. 30, 2014 buildings	Dec. 31, 2013 buildings
Number of properties held for sale in discontinued operations		3	1
Number of properties sold in discontinued operations	2		12	25
Total number of properties in discontinued operations			38
Continuing Operations, Number of In-service Properties Held for Sale			1
Continuing Operations, Number of Real Estate Properties Sold			9	13
Continuing Operations, Number of Real Estate Properties Sold or Classified as Held for Sale			23
Number of Real Estate Properties Held for Sale			2
Number of Real Estate Properties Sold			21	38
Total Properties Sold or Classified as Held for Sale			61
Industrial [Member]
Number of properties held for sale in discontinued operations			0
Number of properties sold in discontinued operations			11	6
Total number of properties in discontinued operations			17
Office [Member]
Number of properties held for sale in discontinued operations			0
Number of properties sold in discontinued operations			0	12
Total number of properties in discontinued operations			12
Medical Office [Member]
Number of properties held for sale in discontinued operations			1
Number of properties sold in discontinued operations			1	6
Total number of properties in discontinued operations			8
Retail [Member]
Number of properties held for sale in discontinued operations			0
Number of properties sold in discontinued operations			0	1
Total number of properties in discontinued operations			1