Prepaid Expenses and Other Current Assets and Other Assets (Schedule Of Other Assets) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Other Assets, Noncurrent [Line Items]
Prepaid ground rent		$ 263,694
Straight-line rent receivable	$ 323,708	322,073
Loan receivables	54,490	49,255
Deferred lease costs, net	4,054	27,020
Deferred tax asset - long term	15,830	18,330
Other	41,527	41,661
Total other assets	439,609	722,033
Accumulated deficit	5,131,347	$ 5,136,368
Accounting Standards Update 2016-02 [Member]
Other Assets, Noncurrent [Line Items]
Accumulated deficit	$ 23,300