COVID-19 Pandemic (Narrative) (Details) - COVID-19 $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($)	Apr. 30, 2021 employee
Unusual or Infrequent Item, or Both [Line Items]
Rent collected, percent	96.00%
Write off of receivables arising from the straight-lining of rents	$ 1,001
Write off of tenant receivables deemed uncollectible	$ 2,910
Office
Unusual or Infrequent Item, or Both [Line Items]
Rent collected, percent	97.00%
Retail
Unusual or Infrequent Item, or Both [Line Items]
Rent collected, percent	90.00%
Building Maintenance Service LLC | Subsequent Event
Unusual or Infrequent Item, or Both [Line Items]
Percentage of employees returned from furlough		70.00%
Number of employees furloughed | employee		1,293