Discontinued Operations, Assets Held for Sale and Impairments (Table Illustration of Number of Properties in Discontinued Operations) (Details)	3 Months Ended		9 Months Ended	12 Months Ended
	Jun. 30, 2014 buildings	Mar. 31, 2014 buildings	Sep. 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			2
Continuing Operations, Number of Real Estate Properties Sold			11	13
Continuing Operations, Number of Real Estate Properties Sold or Classified as Held for Sale			26
Number of Real Estate Properties Held for Sale			3
Number of Real Estate Properties Sold			23	38
Total Properties Sold or Classified as Held for Sale			64
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