Leases and Management Agreements with Five Star - Narrative (Details) $ in Thousands		1 Months Ended	3 Months Ended	12 Months Ended
	Apr. 01, 2019 USD ($)	Jan. 31, 2021 USD ($)	Mar. 31, 2020 community	Dec. 31, 2020 USD ($) lease_agreement trustee community option shares	Dec. 31, 2019 USD ($) community shares	Dec. 31, 2018 USD ($) community	Feb. 01, 2019 USD ($)
Concentration Risk
Common shares, shares issued (in shares) | shares				238,268,478	237,897,163
Gain on lease termination				$ 22,896	$ 0	$ 0
Due from affiliates				0	$ 1,990
Five Star
Concentration Risk
Common shares, shares issued (in shares) | shares					10,268,158
Aggregate shares issued (shares) | shares					16,118,849
Five Star
Concentration Risk
Amounts of transaction				75,000
Gain on lease termination				$ 22,896
Monthly minimum rent payable							$ 11,000
Management fees as a percentage of gross revenues				5.00%
Percentage of annual incentive fee				15.00%
Property management agreement, management fees				1.50%
Business and property management agreement, number of agreements | option				2
Renewal term (years)				5 years
Percentage target EBITDA of new management agreement not earned				90.00%
Percentage target EBITDA of new management agreement not earned for all communities				20.00%
Increase in annual lease rent payable						1,433
Amount of improvements to communities						111,603
Payments to acquire property, plant, and equipment						49,155
Senior Living Communities
Concentration Risk
Real estate improvements by lessee purchased				$ 2,138	$ 1,739
Increase in annual lease rent payable				$ 135	$ 90
Five Star
Concentration Risk
Number of communities leased by the company | community					166
Number of communities managed | community			78
Amounts of transaction					$ 137,898	212,622
Consumer price index annual estimated increase				2.00%
Trigger basis for capital investment ratio (percent)				6.00%
Due from affiliates					1,989	18,697
Real estate improvements by lessee purchased						17,956
Increase in annual lease rent payable						1,433
Expenses from property management agreement transactions with related party				$ 62,880	15,327	14,426
Related party transaction capitalized amount				2,467
Lease income				1,561
Five Star | Property Operating Expense
Concentration Risk
Expenses from property management agreement transactions with related party				60,413
Five Star | Senior Living Communities
Concentration Risk
Expenses from transactions with related party				$ 25,687	5,920	6,442
Five Star
Concentration Risk
Number of leases with related party | lease_agreement				5
Annual rent as a percentage of gross revenues, percent				4.00%
Annual rent as a percentage of gross revenues, amount					$ 538	$ 5,525
Five Star | Subsequent Event
Concentration Risk
Payments made in exchange for customary release		$ 5,763
Refunded management fees		$ 115
Five Star | Senior Living Communities
Concentration Risk
Number of communities managed | community				235	78	76
Number of real estate properties inadequate documentation | trustee				1
Five Star | Senior Living Communities
Concentration Risk
Payments to acquire property, plant, and equipment	$ 49,155
Residents fees and services | SHOP
Concentration Risk
Revenue reserve for inadequate documentation				$ 3,842
Penalties for inadequate documentation				$ 1,921