Variable Interest Entities (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) property joint_venture	Dec. 31, 2017 property center joint_venture
Variable Interest Entity [Line Items]
Number of real estate properties | center		2
Number of VIE's guaranteed by company	1	1
Consolidated Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Number of VIE real estate joint ventures	9	9
Number of real estate properties | property	21	22
Unconsolidated Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Number of VIE real estate joint ventures	2	2
Number of joint venture arrangements	1
Future additional funding | $	$ 57