Property (Schedule Of Property) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Real Estate [Abstract]
Land	$ 991,321	$ 1,068,022
Land held for development	66,949	69,205
Land under development	49,000	48,985
Buildings and improvements	3,151,367	3,232,074
Construction in-progress	107,033	80,573
Total	$ 4,365,670	$ 4,498,859