Investments in Unconsolidated Companies (Summarized Financial Information) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Equity Method Investments and Joint Ventures [Abstract]
Rental revenue	$ 59,905	$ 60,446	$ 71,424
Equity Method Investment, Gain (Loss) on Sale of Properties	24,099	25,879	4,986
Equity Method Investment, Summarized Financial Information, Net Income (Loss)	40,134	44,372	20,673
Equity in earnings (loss) of unconsolidated joint ventures	31,406	21,444	$ 63,310
Land, buildings and tenant improvements, net	305,888	328,959
Construction in progress	7,747	43,892
Undeveloped land	29,518	28,247
Other assets	75,909	88,448
Total assets	419,062	489,546
Indebtedness	129,700	209,584
Other liabilities	24,208	38,172
Total liabilities	153,908	247,756
Owners' equity	265,154	241,790
Total liabilities and equity	419,062	489,546
Investments in and advances to unconsolidated joint ventures	133,074	110,795
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	$ 2,500	$ 11,400