Real Estate - Schedule of Construction in Progress (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Real Estate [Line Items]
Construction in progress	$ 345,880	$ 335,644
Glebe Road
Real Estate [Line Items]
Construction in progress	267,563	255,443
7316 Wisconsin Avenue
Real Estate [Line Items]
Construction in progress	46,946	44,638
Ashbrook Marketplace
Real Estate [Line Items]
Construction in progress	19,796	19,128
Other
Real Estate [Line Items]
Construction in progress	$ 11,575	$ 16,435