Investments in Unconsolidated Companies (Summarized Financial Information) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Equity Method Investments and Joint Ventures [Abstract]
Rental revenue	$ 57,952	$ 59,905	$ 60,446
Gains on land and property sales - continuing operations	2,076	24,099	25,879
Net income	19,183	40,134	44,372
Equity in earnings of unconsolidated joint ventures	11,944	31,406	$ 21,444
Land, buildings and tenant improvements, net	321,803	305,888
Construction in progress	23,507	7,747
Undeveloped land	23,653	29,518
Other assets	79,842	75,909
Total assets	448,805	419,062
Indebtedness	155,539	129,700
Other liabilities	31,946	24,208
Total liabilities	187,485	153,908
Owners' equity	261,320	265,154
Total liabilities and equity	448,805	419,062
Investments in and advances to unconsolidated joint ventures	131,898	133,074
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	$ 2,700	$ 2,500