Business and Property Management Agreements with RMR LLC (Details) $ in Thousands	1 Months Ended	3 Months Ended
	Jan. 31, 2019 USD ($)	Mar. 31, 2019 USD ($) employee agreement	Mar. 31, 2018 USD ($)
Real Estate Properties [Line Items]
Number of employees | employee		0
Amended and restate business management agreement | RMR LLC
Real Estate Properties [Line Items]
Number of management service agreements | agreement		2
Business management fees incurred		$ 9,727	$ 9,724
Incentive fee calculation period		3 years
Incentive fees paid	$ 53,635
Related party property management and construction management fee		$ 11	13
Related party reimbursement expenses		$ 200	$ 135