Schedule III Properties And Accumulated Depreciation (Summary Of Accumulated Depreciation And Amortization) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Balance, beginning of year	$ 2,668,509	$ 2,251,268	$ 1,874,054
Additions during period (depreciation and amortization expense)	612,970	461,506	429,057
Deductions during period (dispositions and assets held for sale)	(43,252)	(44,265)	(51,843)
Balance, end of year	$ 3,238,227	$ 2,668,509	$ 2,251,268