Real Estate Properties - Investments and Capital Expenditures - (Details) ft² in Thousands, $ in Thousands	1 Months Ended	12 Months Ended
	Feb. 28, 2015 USD ($)	Dec. 31, 2016 USD ($) ft²	Dec. 31, 2015 USD ($) ft²	Dec. 31, 2014 USD ($)
Real Estate [Line Items]
Real estate improvements by lessee purchased		$ 21,438	$ 21,444
Leases committed expenditure		$ 12,422	$ 20,314
Area of real estate properties leased (in square feet) | ft²		899,000	1,032,000
Lease committed but unspent tenant related obligations		$ 23,271	$ 30,260
Five Star
Real Estate [Line Items]
Real estate improvements by lessee purchased		21,438	21,444	$ 25,804
Increase or decrease in annual lease rent payable	$ 39	$ 1,719	$ 1,734	$ 2,066