Discontinued Operations and Assets Held for Sale (Table Illustration of Number of Properties in Discontinued Operations) (Details) - buildings	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Number of properties held for sale in discontinued operations	0
Number of properties sold in discontinued operations	0	62	12
Total number of properties in discontinued operations	74
Continuing Operations, Number of In-service Properties Held for Sale	5
Continuing Operations, Number of Real Estate Properties Sold	32	91	17
Continuing Operations, Number of Real Estate Properties Sold or Classified as Held for Sale	145
Number of Real Estate Properties Held for Sale	5
Number of Real Estate Properties Sold	32	153	29
Total Properties Sold or Classified as Held for Sale	219
Industrial [Member]
Number of properties held for sale in discontinued operations	0
Number of properties sold in discontinued operations	0	5	11
Total number of properties in discontinued operations	16
Medical Office [Member]
Number of properties held for sale in discontinued operations	0
Number of properties sold in discontinued operations	0	1	1
Total number of properties in discontinued operations	2
Other Segments [Member]
Number of properties held for sale in discontinued operations	0
Number of properties sold in discontinued operations	0	56	0
Total number of properties in discontinued operations	56