Discontinued Operations and Assets Held for Sale (Table Illustration of Number of Properties in Discontinued Operations) (Details)	1 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2019 buildings	Dec. 31, 2018 buildings	Dec. 31, 2017 buildings
Number of properties held for sale in discontinued operations		0
Number of properties sold in discontinued operations		0	0	81
Total number of properties in discontinued operations		81
Continuing Operations, Number of In-service Properties Held for Sale		1
Continuing Operations, Number of Real Estate Properties Sold		28	15	17
Continuing Operations, Number of Real Estate Properties Sold or Classified as Held for Sale		61
Number of Real Estate Properties Held for Sale		1
Number of Real Estate Properties Sold	18	28	15	98
Total Properties Sold or Classified as Held for Sale		142
Industrial [Member]
Number of properties held for sale in discontinued operations		0
Number of properties sold in discontinued operations		0	0	0
Total number of properties in discontinued operations		0
Non-reportable segments
Number of properties held for sale in discontinued operations		0
Number of properties sold in discontinued operations		0	0	81
Total number of properties in discontinued operations		81
Medical Office Portfolio Sale [Member]
Number of Real Estate Properties Sold				85