Related Parties (Narrative) (Details) $ in Thousands		1 Months Ended				12 Months Ended
	Feb. 12, 2016 USD ($)	Nov. 30, 2016 USD ($) joint_venture	Oct. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Feb. 29, 2016 USD ($) center	Dec. 31, 2016 USD ($) property center	Dec. 31, 2015 USD ($) center	Dec. 31, 2014 USD ($)
Related Party Transaction [Line Items]
Net accounts receivable, related parties						$ 2,200	$ 1,200
Accounts payable and accrued expenses, related parties						300	5,200
Management fees revenues, related parties						5,100	4,500	$ 4,600
Payments to acquired interest in joint ventures						$ 52,834	$ 30,053	$ 5,223
Number of real estate properties | center						2	2
Assets held by joint venture						$ 4,426,928	$ 3,901,945
Debt held by joint venture						$ 2,034,998
Proceeds from business acquisition					$ 2,500
Number of centers sold					1	12
51% Owned Real Estate joint venture [Member]
Related Party Transaction [Line Items]
Equity interest in joint venture (percent)							51.00%
Number of real estate properties | center							3
Assets held by joint venture							$ 43,700
Debt held by joint venture							$ 72,400
Consolidated Joint Venture [Member]
Related Party Transaction [Line Items]
Number of real estate join ventures acquired | joint_venture		2
Payments to acquired interest in joint ventures		$ 3,300
Series of Individually Immaterial Business Acquisitions [Member]
Related Party Transaction [Line Items]
Percentage of voting interest acquired				50.00%		50.00%
Equity interest in joint venture				$ 13,500		$ 13,579
Gain recognized on equity interest remeasured to fair value				$ 9,000
Business Combination Achieved in Stages [Member]
Related Party Transaction [Line Items]
Percentage of voting interest acquired	49.00%				49.00%
Equity interest in joint venture	$ 22,514
Proceeds from business acquisition	2,500
Gain recognized on equity interest remeasured to fair value	$ 37,383
Joint Venture [Member] | Repayments of Notes Payable [Member]
Related Party Transaction [Line Items]
Increase (Decrease) in Accounts Payable, Related Parties						$ 4,800
Distribution of Nonmonetary Assets to Groups of Stockholders’ in Lieu of Capital Return Cash Distributions [Member] | Unconsolidated Real Estate Joint Venture [Member]
Related Party Transaction [Line Items]
Nonmonetary Transaction, Gain (Loss) Recognized on Transfer			$ 1,900