Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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- Definition

Amount of real estate investment property which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; and (7) other real estate investments.

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Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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Leases and Management Agreements with Five Star - Schedule of Assets Leased and Revenues Earned (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Concentration Risk
Gross Book Value of Real Estate Assets	$ 7,410,730	$ 7,461,586
Total revenues	$ 1,632,026	1,040,155	$ 1,117,164
Real Estate Investment Property At Cost \| Rents from significant lessee
Concentration Risk
Gross Book Value of Real Estate Assets		$ 8,420,623	$ 8,428,644
Concentration of credit risk (as a percent)		100.00%	100.00%
Revenue \| Senior Living Communities
Concentration Risk
Total revenues		$ 433,597	$ 416,523
Revenue \| Rents from significant lessee
Concentration Risk
Concentration of credit risk (as a percent)		100.00%	100.00%
Total revenues		$ 1,040,155	$ 1,117,164
Five Star \| Real Estate Investment Property At Cost \| Rents from significant lessee
Concentration Risk
Gross Book Value of Real Estate Assets		$ 2,286,951	$ 2,253,853
Concentration of credit risk (as a percent)		27.20%	26.70%
Five Star \| Real Estate Investment Property At Cost \| Rents from significant lessee \| Discontinued Operations, Held-for-sale
Concentration Risk
Gross Book Value of Real Estate Assets		$ 50,951
Five Star \| Real Estate Investment Property At Cost \| Rents from significant lessee \| Senior Living Communities
Concentration Risk
Gross Book Value of Real Estate Assets		$ 1,920,070
Five Star \| Revenue \| Rents from significant lessee
Concentration Risk
Concentration of credit risk (as a percent)		13.30%	19.00%
Total revenues		$ 137,898	$ 212,622
All others \| Real Estate Investment Property At Cost \| Rents from significant lessee
Concentration Risk
Gross Book Value of Real Estate Assets		$ 6,133,672	$ 6,174,791
Concentration of credit risk (as a percent)		72.80%	73.30%
All others \| Real Estate Investment Property At Cost \| Rents from significant lessee \| Discontinued Operations, Held-for-sale
Concentration Risk
Gross Book Value of Real Estate Assets		$ 213,416	$ 3,752
All others \| Revenue \| Rents from significant lessee
Concentration Risk
Concentration of credit risk (as a percent)		86.70%	81.00%
Total revenues		$ 902,257	$ 904,542