Schedule III Properties And Accumulated Depreciation (Summary Of Historical Cost) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
SEC Schedule III, Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Balance, beginning of year	$ 11,558,469	$ 10,915,373	$ 9,982,612
Additions during period (acquisitions and improvements)	5,663,404	760,051	1,133,263
Deductions during period (dispositions, impairments and assets held for sale)	(305,937)	(116,955)	(200,502)
Balance, end of year	$ 16,915,936	$ 11,558,469	$ 10,915,373