Shareholders' Equity (Details) - USD ($) $ in Thousands		12 Months Ended
	Apr. 12, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Officers and employees of RMR
Common Share Issuances
Common shares granted under equity compensation plan (in shares)		140,100	97,000	85,000
Stock granted value		$ 3,507	$ 2,810	$ 2,387
Trustees | Common Shares
Common Share Issuances
Common shares granted under equity compensation plan (in shares)	3,000	3,000	3,000	3,000
Stock granted value	$ 75	$ 370	$ 427	$ 452
Stock granted value per trustee		$ 74	$ 85	$ 90