Related Parties (Narrative) (Details) $ in Thousands		3 Months Ended		6 Months Ended
	Feb. 12, 2016 USD ($) center	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) property	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($) center
Related Party Transaction [Line Items]
Net accounts receivable, related parties		$ 1,600		$ 1,600		$ 1,200
Accounts payable and accrued expenses, related parties		5,200		5,200		5,200
Management fees revenues, related parties		1,100	$ 1,100	2,300	$ 2,300
Total assets		4,032,927		4,032,927		$ 3,901,945
Debt, net		$ 1,871,510		$ 1,871,510
Business acquisition, percentage of voting interests acquired	49.00%
Proceeds to acquire businesses, gross	$ 2,500
Number of operating properties sold	1			3
51% Owned Real Estate joint venture [Member]
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	$ 37,400