Real Estate And Accumulated Depreciation (Changes In Accumulated Depreciation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Balance at beginning of year	$ 1,184,546	$ 1,087,642	$ 1,028,619
Additions at cost	132,900	131,120	120,426
Retirements or sales	(127,391)	(33,132)	(42,603)
Property held for sale	(23,929)	(1,084)	(18,800)
Balance at end of year	$ 1,166,126	$ 1,184,546	$ 1,087,642