Related Parties (Narrative) (Details) $ in Thousands		3 Months Ended
	Feb. 12, 2016 USD ($) center	Mar. 31, 2016 USD ($) property	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($) center
Related Party Transaction [Line Items]
Net accounts receivable, related parties		$ 1,300		$ 1,200
Accounts payable and accrued expenses, related parties		5,400		5,200
Management fees revenues, related parties		1,200	$ 1,200
Total assets		4,033,840		$ 3,901,945
Debt, net		$ 1,924,052
Number of operating properties sold	1	3
Business acquisition, percentage of voting interests acquired	49.00%
Proceeds to acquire businesses, gross	$ 2,500
51% Owned Real Estate joint venture [Member] | Equity Method Investee
Related Party Transaction [Line Items]
Equity interest in acquiree, percentage				51.00%
Number of real estate properties | center				3
Total assets				$ 43,700
Debt, net				$ 72,400
Business Combination Achieved in Stages [Member]
Related Party Transaction [Line Items]
Business acquisition, percentage of voting interests acquired	49.00%
Proceeds to acquire businesses, gross	$ 2,500
Gain recognized on equity interest remeasured to fair value	$ 37,383