Variable Interest Entities (Narrative) (Details) $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	May. 31, 2015 USD ($)	Mar. 31, 2016 joint_venture property	Dec. 31, 2015 property joint_venture
Variable Interest Entity [Line Items]
Number of VIE real estate joint ventures			1
Number of VIE real estate joint ventures guaranteed by company		1
Consolidated Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Number of VIE real estate joint ventures		11	11
Number of neighborhood/community shopping centers | property		30	30
Joint venture amendment, additional contribution | $	$ 43
Unconsolidated Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Number of VIE real estate joint ventures		1	1