Investments in Partially Owned Entities (Summary of Condensed Combined Financial Information) (Details) - Partially Owned Properties - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Assets	$ 24,812	$ 24,926
Liabilities	22,739	21,357
Noncontrolling interests	140	265
Equity	1,933	3,304
Total revenue	12,991	13,600	$ 13,423
Net loss	$ (542)	$ (65)	$ (224)