Business and Property Management Agreements with RMR (Details) - RMR LLC $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($) agreement employee	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Related Party Transaction [Line Items]
Number of employees | employee	0
Number of agreements with RMR LLC to provide management services | agreement	2
Net business management fees		$ 18,637	$ 17,358
Recognized amortization of the liability	$ 603	603	603
Management fees as percentage of gross collected rents	3.00%
Construction supervision fees as percentage of construction costs	5.00%
Reimbursement amounts	$ 24,371	24,766	24,919
Net Property Management and Construction Supervision Fees
Related Party Transaction [Line Items]
Net business management fees	17,376
Transaction amount	25,756	21,103	20,774
Reimbursement amounts	484	484	484
Net Property Management and Construction Supervision Fees | Investment Building and Building Improvements
Related Party Transaction [Line Items]
Transaction amount	9,917	4,596	3,446
Net Property Management and Construction Supervision Fees | Other Operating Income (Expense)
Related Party Transaction [Line Items]
Transaction amount	$ 15,839	$ 16,507	$ 17,328
Transition Services
Related Party Transaction [Line Items]
Duration of transition services	120 days
Amended And Restate Business Management Agreement
Related Party Transaction [Line Items]
Percentage applied on average historical cost of real estate investment properties acquired	0.50%
Base management fee payable as percentage of average historical cost of real estate investments	0.70%
Percentage of average closing stock price on stock exchange	0.70%
Management fee payable as percentage of average market capitalization exceeding specified amount	0.50%
Percentage for limitation and adjustments of incentive management fee payable	12.00%
Measurement period for incentive management fee	3 years
Average closing price of our common shares, consecutive trading days	10 days
Highest average closing price of our common shares, final consecutive trading days	30 days
Percentage for limitation and adjustments of incentive management fee payable, minimum total return per share percentage change	5.00%
Percentage of base business management fee payable in common shares	1.50%
Amended And Restate Business Management Agreement | Up C Transaction
Related Party Transaction [Line Items]
Written notice for convenience	60 days
Window of written notice after calendar year	60 days
Window for written notice after change of control	12 months
Remaining termination fee term	10 years
Amended And Restate Business Management Agreement | Maximum
Related Party Transaction [Line Items]
Threshold amount of real estate investments	$ 250,000
Threshold amount of average market capitalization	$ 250,000
Percentage for limitation and adjustments of incentive management fee payable, total return per share percentage, reduction	5.00%
Amended And Restate Business Management Agreement | Maximum | Up C Transaction
Related Party Transaction [Line Items]
Termination fee term	20 years
Amended And Restate Business Management Agreement | Minimum
Related Party Transaction [Line Items]
Threshold amount of real estate investments	$ 250,000
Base management fee payable average market capitalization	$ 250,000
Percentage for limitation and adjustments of incentive management fee payable, total return per share percentage, reduction	2.00%
Amended And Restate Business Management Agreement | Minimum | Up C Transaction
Related Party Transaction [Line Items]
Termination fee term	19 years