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Shareholders' Equity - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands			12 Months Ended
	Jan. 13, 2022	Jan. 01, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Scheduled to vest unvested shares
Share-based compensation expense			$ 1,960	$ 1,568	$ 1,388
Distributions to shareholders			$ 9,540	$ 42,825	$ 199,719
ALR
Scheduled to vest unvested shares
Aggregate shares issued (shares)		16,118,849
Subsequent Event
Scheduled to vest unvested shares
Common distributions declared (in dollars per share)	$ 0.01
Distributions to shareholders	$ 2,390
Certain our Officers and Employees of RMR LLC
Scheduled to vest unvested shares
Shares purchased from certain of our officers and other employees of RMR LLC (in shares)			109,384	47,375	31,747
ALR
Share-based Compensation Arrangement by Share-based Payment Award
Aggregate market value of shares awarded		$ 59,801
Share Award Plans
Share-based Compensation Arrangement by Share-based Payment Award
Remaining common shares available for issuance (in shares)			1,117,201
Number of unvested shares (in shares)			845,620	434,550	227,340	161,990
Scheduled to vest unvested shares
2022 (in shares)			253,520
2023 (in shares)			239,700
2024 (in shares)			208,800
2025 (in shares)			143,600
Estimated future compensation for the unvested shares			$ 3,116
Weighted average period over which the compensation expense will be recorded			2 years
Officers and Employees | Share Award Plans | RMR LLC
Share-based Compensation Arrangement by Share-based Payment Award
Common shares awarded (in shares)			718,000	360,000	187,500
Aggregate market value of shares awarded			$ 2,448	$ 1,357	$ 1,633
Award vesting period			5 years
Trustees | Share Award Plans | RMR LLC
Share-based Compensation Arrangement by Share-based Payment Award
Common shares awarded (in shares)			20,000	10,000	3,000
Aggregate market value of shares awarded			$ 444	$ 176	$ 119
Market value of shares awarded to each Trustee			$ 74	$ 29	$ 24

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