Significant Acquisitions and Dispositions (Summary of Significant Assumptions Utilized in Estimates) (Details)	Dec. 31, 2020 buildings $ / sqft	Dec. 31, 2019 buildings $ / sqft	Dec. 31, 2018 buildings
Number of Real Estate Properties | buildings	10	6	9
Industrial [Member] | Minimum [Member]
Fair Value Measurement With Unobservable Inputs Rental Rate Per Square Foot	5.28	5.90
Industrial [Member] | Maximum [Member]
Fair Value Measurement With Unobservable Inputs Rental Rate Per Square Foot	18.11	15.60
Measurement Input, Cap Rate [Member] | Minimum [Member]
Fair Value Inputs, Capitalization Rate	3.98%	4.23%
Measurement Input, Cap Rate [Member] | Maximum [Member]
Fair Value Inputs, Capitalization Rate	5.46%	5.32%