Real Estate And Accumulated Depreciation (Total Cost Of The Properties) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Balance at beginning of year	$ 4,145,249	$ 4,105,068	$ 4,498,859
Additions at cost	311,789	389,858	164,150
Retirements or sales	(186,551)	(349,603)	(547,821)
Impairment loss	(24,153)	(74)	(10,120)
Balance at end of year	$ 4,246,334	$ 4,145,249	$ 4,105,068