Investments in Unconsolidated Joint Ventures - Narrative (Details) - Joint Venture - USD ($) $ in Thousands	Dec. 18, 2019	Aug. 16, 2019	Jul. 25, 2019	Sep. 12, 2019
Fashion District Philadelphia
Schedule of Equity Method Investments [Line Items]
Additional borrowings			$ 100,000
Interest rate spread over basis			2.00%
Amount of additional borrowing		$ 25,000	$ 26,000
Tysons Tower
Schedule of Equity Method Investments [Line Items]
New loan				$ 190,000
Effective interest rate				3.38%
One Westside | Construction loan
Schedule of Equity Method Investments [Line Items]
Amount of additional borrowing	$ 414,600
One Westside | Construction loan | LIBOR
Schedule of Equity Method Investments [Line Items]
Interest rate spread over basis	1.70%
Variable interest rate spread, contingent (as a percent)	1.50%