Accounts Receivable, Net (Schedule Of Accounts Receivable) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Development in Process	$ 249,931	$ 257,629
Revenue Bond Receivable	11,423	14,718
Straight-line rent receivable	65,203	62,605
Allowance for doubtful accounts	(8,437)	(7,485)
Total	88,750	93,693
Rental properties, net of accumulated depreciation of $776,404 and $741,334 at March 31, 2018 and December 31, 2017, respectively	4,815,137	4,604,231
Land Available for Development	33,693	33,692
Tenants [Member]
Carrying amounts of accounts receivable	16,642	19,923
Non-Tenants [Member]
Carrying amounts of accounts receivable	3,919	3,932
early childhood education center [Member] | Tenants [Member]
Development in Process	14,700
Total	6,700	$ 6,000
Rental properties, net of accumulated depreciation of $776,404 and $741,334 at March 31, 2018 and December 31, 2017, respectively	253,600
Land Available for Development	$ 11,200