Investments in Partially Owned Entities (Urban Edge Properties and PREIT) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Schedule Of Equity Method Investments
Net gain resulting from operating partnership unit issuances	$ (5,200)		$ (21,100)
UE
Schedule Of Equity Method Investments
Equity method ownership percentage	4.50%		4.50%		5.40%
Closing share price (in dollars per share)	$ 24.12		$ 24.12
Equity method investment fair value	$ 137,898		$ 137,898
Excess of investee's fair value over carrying amount	91,356		91,356
Net gain resulting from operating partnership unit issuances	$ 5,200	$ 0	$ 21,100	$ 0
PREIT
Schedule Of Equity Method Investments
Ownership common shares, investee (in shares)	6,250,000		6,250,000
Equity method ownership percentage	8.00%		8.00%
Closing share price (in dollars per share)	$ 10.49		$ 10.49
Reporting unit, amount of fair value in excess of carrying amount	$ 44,465		$ 44,465
Non cash impairment losses	44,465		44,465
Excess of investee's carrying amount over equity in net assets	33,399		33,399
Level 1 | Nonrecurring | PREIT
Schedule Of Equity Method Investments
Equity method investment fair value	$ 65,563		$ 65,563
Partnership Interest | UE
Schedule Of Equity Method Investments
Ownership common shares, investee (in shares)	5,717,184		5,717,184
Operating partnership units issued	6,250,000		20,250,000