Basis of Presentation and Significant Accounting Policies (Narratives) (Details)	6 Months Ended	12 Months Ended
	Jun. 30, 2015 USD ($)	Dec. 31, 2016 USD ($) swaps	Dec. 31, 2015 USD ($) swaps	Dec. 31, 2014 USD ($)
Basis of Presentation and Significant Accounting Policies
Number of interest rate swaps | swaps		2	1
Real Estate
Capitalized interest and debt expense during construction		$ 34,097,000	$ 59,305,000
Schedule Of Equity Method Investments
Non cash impairment losses		$ 20,290,000	21,260,000	$ 85,459,000
Minimum Percentage of Taxable Income Distributed As Dividends		90.00%
Percentage Of Taxable Income Distributed		100.00%
Allowance for Doubtful Accounts
Tenant and other receivables, allowance for doubtful accounts (in US dollars)		$ 10,920,000	11,908,000
Receivables Arising From Straight Lining Of Rents Allowance		2,227,000	2,751,000
Tax Treatment of Dividend
Income Tax Liability Relating to Taxable REIT Subsidiaries Current		7,946,000	8,322,000	10,777,000
Deferred tax assets related to net operating loss carryforward		98,013,000	97,104,000
Reversal of allowance for deferred tax assets	$ (90,030,000)	$ 0	$ (90,030,000)	0
Toys R Us
Schedule Of Equity Method Investments
Non cash impairment losses				$ 75,196,000
Ordinary Income
Schedule Of Equity Method Investments
Percentage Of Taxable Income Distributed		83.50%
Long Term Capital Gain
Schedule Of Equity Method Investments
Percentage Of Taxable Income Distributed		16.50%
Minimum
Property Plant And Equipment
Real Estate And Accumulated Depreciation Life Used For Depreciation		7 years
Maximum
Property Plant And Equipment
Real Estate And Accumulated Depreciation Life Used For Depreciation		40 years