Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Commitments and Contingencies
Contingent liabilities for construction performance	$ 2.4	$ 4.3
Rental Revenues | Hampton Roads Properties
Commitments and Contingencies
Concentrations of credit risk	44.00%	48.00%	53.00%
Rental Revenues | Town Center Properties
Commitments and Contingencies
Concentrations of credit risk	27.00%	31.00%	38.00%
Operating Partnership
Commitments and Contingencies
Outstanding letters of credit	$ 9.5	$ 9.5
Group Of Three Construction Customers | General Contracting and Real Estate Services Revenues
Commitments and Contingencies
Concentrations of credit risk	65.00%	67.00%	55.00%
Group Of Three Construction Customers | General Contracting and Real Estate Services Segment Profit
Commitments and Contingencies
Concentrations of credit risk	72.00%	66.00%	28.00%