Real Estate And Accumulated Depreciation (Total Cost Of The Properties) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Balance at beginning of year	$ 4,498,859	$ 4,789,145	$ 4,262,959
Additions at cost	164,150	137,462	654,513
Retirements or sales	(547,821)	(334,105)	(126,666)
Property held for sale	0	(78,721)	(1,563)
Impairment loss	(10,120)	(14,922)	(98)
Balance at end of year	$ 4,105,068	$ 4,498,859	$ 4,789,145