Acquisitions (Purchase Price Allocation) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Feb. 12, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Land	$ 505,228		$ 485,560
Dallas Galleria Office Towers
Property, Plant and Equipment [Line Items]
Land		$ 19,674
Building and improvements		293,760
Intangible lease assets		49,177
Lease acquisition costs, net of tenant credits received from seller		1,344
Intangible lease organization costs		55,060
Intangible lease liabilities		(22,169)
Total purchase price		$ 396,846
Acquired intangible assets, remaining amortization period	5 years 2 months 12 days