Business and Property Management Agreements with RMR LLC (Details)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020 USD ($) employee agreement	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) employee agreement	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Related Party Transaction [Line Items]
Number of employees | employee	0		0
Business management fees	$ 347,000		$ 476,000
Incentive fee expense					$ 0
Reit Management And Research L L C
Related Party Transaction [Line Items]
Number of management service agreements | agreement	2		2
Business management fees	$ 3,277,000	$ 3,092,000	$ 6,584,000	$ 5,285,000
Construction supervision fees	1,860,000	1,922,000	3,783,000	3,269,000
Related party reimbursement expense	$ 1,217,000	$ 1,026,000	$ 2,416,000	$ 1,929,000