Represents the number of agreements with RMR LLC to provide management services to the company.

No definition available.

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- Definition

Represents the number of entities to whom related party provides management services.

+ References

No definition available.

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- Definition

This element represents the aggregate cost of investments accounted for under the equity method of accounting.

+ References

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- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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- Definition

Expenses recognized resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party.

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- Definition

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.

+ References

No definition available.

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Amount of revenue, fees and commissions earned from transactions between (a) a parent company and its subsidiaries; (b) subsidiaries of a common parent; (c) an entity and trusts for the benefit of employees, for example, but not limited to, pension and profit-sharing trusts that are managed by or under the trusteeship of the entity's management; (d) an entity and its principal, owners, management, or members of their immediate families; and (e) affiliates.

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- Definition

For net-share settlement of share-based awards when the employer settles employees' income tax withholding obligations, this element represents the number of shares the employees use to repay the employer.

+ References

No definition available.

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- Definition

Number of new stock issued during the period.

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- Definition

Cumulative number of shares issued or sold by the subsidiary or equity method investee on all stock transactions.

+ References

No definition available.

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Related Person Transactions - REITs, for which RMR LLC provides Management Services (Details) $ in Thousands		1 Months Ended		3 Months Ended		9 Months Ended
	Sep. 13, 2018 shares	Sep. 30, 2018 USD ($) company shares	Sep. 30, 2017 shares	Sep. 30, 2018 USD ($) company	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) agreement company shares	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
SIR
Related Party Transaction [Line Items]
Shares holding (in shares) \| shares	24,918,421					24,918,421
Percentage of outstanding shares owned		27.80%		27.80%		27.80%
RMR Inc \| Class A common shares
Related Party Transaction [Line Items]
Shares holding (in shares) \| shares						1,214,225
RMR LLC
Related Party Transaction [Line Items]
Number of agreements \| agreement						2
Revenue from related party \| $				$ 263	$ 90	$ 763	$ 272
Property insurance premiums paid \| $				$ 20,575	$ 1,891	$ 30,059	$ 8,241
AIC
Related Party Transaction [Line Items]
Number of entities to whom services are provided \| company		4		4		4
Carrying value of equity method investments \| $		$ 9,276		$ 9,276		$ 9,276		$ 8,304
Property Insurance Premium Expense
Related Party Transaction [Line Items]
Property insurance premiums paid \| $						$ 1,211
Officers and Other Employees
Related Party Transaction [Line Items]
Shares paid for tax withholding (in shares) \| shares		18,875	13,636
Common shares \| Officers and Other Employees
Related Party Transaction [Line Items]
Common shares issued (in shares) \| shares		58,700	57,350