Investments in Partially Owned Entities (Independence Plaza and Toys R Us) (Details)	1 Months Ended	3 Months Ended
	Dec. 31, 2012 USD ($)	Mar. 31, 2018 USD ($) building unit	Mar. 31, 2017 USD ($)
Schedule Of Equity Method Investments
Noncontrolling interests in controlling subsidiaries		$ (8,274,000)	$ 6,737,000
Independence Plaza
Schedule Of Equity Method Investments
Equity method ownership percentage		50.10%
Number of buildings | building		3
Number of units | unit		1,327
Real estate transfer tax	$ 1,730,000
Additional real estate transfer tax		$ 13,103,000
Noncontrolling interests in controlling subsidiaries		$ 6,538,000
Toys R Us
Schedule Of Equity Method Investments
Equity method ownership percentage		32.50%
Equity method investment, carrying amount		$ 0
Tax basis of investments, cost for income tax purposes		420,000,000
Transaction Related Costs and Other | Independence Plaza
Schedule Of Equity Method Investments
Additional real estate transfer tax		$ 13,103,000