Real Estate And Accumulated Depreciation (Total Cost Of The Properties) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Balance at beginning of year	$ 4,105,068	$ 4,498,859	$ 4,789,145
Additions at cost	389,858	164,150	137,462
Retirements or sales	(349,603)	(547,821)	(334,105)
Property held for sale	0	0	(78,721)
Impairment loss	(74)	(10,120)	(14,922)
Balance at end of year	$ 4,145,249	$ 4,105,068	$ 4,498,859