Real Estate And Accumulated Depreciation (Changes In Accumulated Depreciation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Balance at beginning of year	$ 1,110,675	$ 1,108,188	$ 1,166,126
Additions at cost	119,948	109,825	118,664
Retirements or sales	(68,653)	(107,338)	(176,602)
Balance at end of year	$ 1,161,970	$ 1,110,675	$ 1,108,188