Real Estate Properties - Summary of Balance Sheet Information for all Properties Classified as Held for sale (Details) - USD ($) $ in Thousands	Mar. 31, 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	$ 1,153	$ 1,840
Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Real estate properties	24,786	76,066
Rents receivable	7,245	13,270
Other assets, net	6,851	8,352
Assets held for sale	38,882	97,688
Accounts payable and accrued expenses	1,099	1,021
Rent collected in advance	1	408
Security deposits	53	411
Liabilities related to properties held for sale	$ 1,153	$ 1,840