Real Estate Properties - Summary of Balance Sheet Information for all Properties Classified as Held for sale (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Liabilities related to properties held for sale	$ 0	$ 1,840
Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Real estate properties		76,066
Rents receivable		13,270
Other assets, net		8,352
Assets held for sale		97,688
Accounts payable and accrued expenses		1,021
Rent collected in advance		408
Security deposits		411
Liabilities related to properties held for sale		$ 1,840

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