Significant Accounting Policies (Schedule Of Rental Property Improvements) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Land held for development (including pre-development costs)	$ 465,930	$ 483,432
Development and construction in progress, including land	327,039	535,971
Total	792,969	1,019,403
Buildings and improvement	204,900	188,100
Development [Member]
Property, Plant and Equipment [Line Items]
Land	$ 49,600	$ 77,000