Variable Interest Entities (Narrative) (Details) $ in Thousands		1 Months Ended	9 Months Ended	12 Months Ended
		May 31, 2015 USD ($)	Sep. 30, 2016 USD ($) joint_venture property	Dec. 31, 2015 USD ($) property joint_venture
Variable Interest Entity [Line Items]
Number of VIE real estate joint ventures guaranteed by company | joint_venture			1
Acquired property net book value | $	[1]		$ 485,458	$ 240,689
Consolidated Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Number of VIE real estate joint ventures | joint_venture			11	11
Number of neighborhood/community shopping centers | property			29	30
Acquired property net book value | $			$ 250,000
Joint venture amendment, additional contribution | $		$ 43,000
Unconsolidated Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Number of VIE real estate joint ventures | joint_venture			1	1

[1] * Consolidated variable interest entities' assets and debt included in the above balances (see Note 15):