Basis of Presentation and Summary of Significant Accounting Policies (Details Textual) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Deferred tax asset valuation allowance, increase (decrease), amount	$ (11,300)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	138,940	$ 142,541	$ 133,381	$ 131,150
Wholly And Partially Owned Consolidated Properties [Member] | Assets Held-for-sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 400