Unconsolidated Joint Ventures (Management Fees) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Schedule of Equity Method Investments [Line Items]
Asset and property management fees	$ 4,300	$ 1,900
Corporate Joint Venture
Schedule of Equity Method Investments [Line Items]
Asset and property management fees	2,153	1,869
Market Square Joint Venture | Corporate Joint Venture
Schedule of Equity Method Investments [Line Items]
Asset and property management fees	574	568
University Circle Joint Venture | Corporate Joint Venture
Schedule of Equity Method Investments [Line Items]
Asset and property management fees	587	574
333 Market Street Joint Venture | Corporate Joint Venture
Schedule of Equity Method Investments [Line Items]
Asset and property management fees	214	207
1800 M Street Joint Venture | Corporate Joint Venture
Schedule of Equity Method Investments [Line Items]
Asset and property management fees	555	520
799 Broadway Joint Venture | Corporate Joint Venture
Schedule of Equity Method Investments [Line Items]
Asset and property management fees	$ 223	$ 0