Discontinued Operations and Assets Held for Sale (Table Illustration of Number of Properties in Discontinued Operations) (Details) - buildings	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Number of properties held for sale in discontinued operations	0
Number of properties sold in discontinued operations	62	12
Total number of properties in discontinued operations	74
Continuing Operations, Number of In-service Properties Held for Sale	1
Continuing Operations, Number of Real Estate Properties Sold	78	17
Continuing Operations, Number of Real Estate Properties Sold or Classified as Held for Sale	96
Number of Real Estate Properties Held for Sale	1
Number of Real Estate Properties Sold	140	29
Total Properties Sold or Classified as Held for Sale	170
Industrial [Member]
Number of properties held for sale in discontinued operations	0
Number of properties sold in discontinued operations	5	11
Total number of properties in discontinued operations	16
Office [Member]
Number of properties held for sale in discontinued operations	0
Number of properties sold in discontinued operations	56	0
Total number of properties in discontinued operations	56
Medical Office [Member]
Number of properties held for sale in discontinued operations	0
Number of properties sold in discontinued operations	1	1
Total number of properties in discontinued operations	2