Accounts Receivable, Net (Schedule Of Accounts Receivable) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Rental properties, net of accumulated depreciation of $741,334 and $635,535 at December 31, 2017 and 2016, respectively	$ 4,604,231	$ 3,595,762
Insurance Settlements Receivable	0	1,967
Revenue Bond Receivable	14,718	22,164
Straight-line rent receivable	62,605	67,618
Total	93,693	98,939
Land held for development	33,692	22,530
Development in Process	257,629	297,110
Tenants [Member]
Accounts receivable, gross	19,923	7,564
Non-Tenants [Member]
Accounts receivable, gross	3,932	497
Accounts Receivable [Member]
Allowance for doubtful accounts	$ (7,485)	$ (871)
Children's Learning Adventure USA, LLC [Member]
number of leases terminated	9
Rental properties, net of accumulated depreciation of $741,334 and $635,535 at December 31, 2017 and 2016, respectively	$ 255,700
Straight line rent write off	9,000
Accounts receivable, gross	6,000
Land held for development	11,200
Development in Process	$ 14,500
completed early childhood education properties [Member] | Children's Learning Adventure USA, LLC [Member]
number of leases terminated	7
Land held for development [Member] | Children's Learning Adventure USA, LLC [Member]
number of leases terminated	2