Real Estate Properties - Summary of Balance Sheet Information for all Properties Classified as Held for sale (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Liabilities related to properties held for sale	$ 20,336	$ 0
Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Real estate properties	341,263
Acquired real estate leases	13,238
Other assets, net	6,280
Properties held for sale	360,781
Accounts payable and accrued expenses	12,387
Assumed real estate lease obligations	6,516
Rent collected in advance	113
Security deposits	1,320
Liabilities related to properties held for sale	$ 20,336