Real Estate And Accumulated Depreciation (Total Cost Of The Properties) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013	Dec. 31, 2012
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Balance at beginning of year	$ 4,289,276		$ 4,399,850	$ 4,688,526
Additions at cost	144,474		279,624	310,454
Retirements or sales	(348,221)		(232,823)	(608,466)
Property held for sale	(9,435)		(155,017)	0
Property transferred from held for sale	0		0	18,090
Impairment loss	0		(2,358)	(8,754)
Balance at end of year	$ 4,076,094	[1]	$ 4,289,276	$ 4,399,850

[1] The book value of our net fixed asset exceeds the tax basis by approximately $32.0 million at December 31, 2014