Real Estate Properties - Summary of Balance Sheet Information for all Properties Classified as Held for sale (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Liabilities related to properties held for sale	$ 2,019	$ 0
Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Real estate properties	300,840
Acquired real estate leases	147
Rents receivable, net of allowance for doubtful accounts of $66	25,907
Other assets, net	21,309
Assets held for sale	348,203
Accounts payable and accrued expenses	1,054
Rent collected in advance	109
Security deposits	856
Liabilities related to properties held for sale	2,019
Rents receivable, allowance for doubtful accounts	$ 66