Real Estate And Accumulated Depreciation (Total Cost Of The Properties) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Balance at beginning of year	$ 4,076,094	$ 4,289,276	$ 4,399,850
Additions at cost	319,789	144,474	279,624
Retirements or sales	(79,608)	(348,221)	(232,823)
Property held for sale	(53,163)	(9,435)	(155,017)
Impairment loss	(153)	0	(2,358)
Balance at end of year	$ 4,262,959	$ 4,076,094	$ 4,289,276