Schedule III Properties And Accumulated Depreciation (Summary Of Historical Cost) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
SEC Schedule III, Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Balance, beginning of year	$ 10,915,373	$ 9,982,612	$ 9,879,578
Additions during period (acquisitions and improvements)	760,051	1,133,263	560,307
Deductions during period (dispositions, impairments and assets held for sale)	(116,955)	(200,502)	(457,273)
Balance, end of year	$ 11,558,469	$ 10,915,373	$ 9,982,612