Business and Property Management Agreements with RMR LLC (Details) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) employee agreement	Sep. 30, 2017 USD ($)
RMR LLC
Related Party Transaction [Line Items]
Number of employees \| employee			0
Number of agreements \| agreement			2
Related party expense	$ 20,575	$ 1,891	$ 30,059	$ 8,241
Reimbursement expense	5,100	3,436	15,121	10,482
Internal audit costs	50	67	173	202
Net Property Management and Construction Supervision Fees \| RMR LLC
Related Party Transaction [Line Items]
Related party transaction amount	3,415	2,338	10,201	$ 7,371
RMR LLC \| Affiliated Entity
Related Party Transaction [Line Items]
Reversal of expense with related party	$ 16,236	$ (893)	$ 16,973
Period of common share total return, incentive fees payable	3 years

Incentive Fees Payable Based On Common Share Total Return, Duration

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- Definition

Internal Audit Costs

+ References

No definition available.

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- Definition

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

+ References

No definition available.

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Represents the number of employees in the company.

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- Definition

Total expense amount to reimburse a related party.

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- Definition

Amount of expense for incentive rights held by the managing member or general partner, of limited liability company (LLC) or limited partnership (LP).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Topic 850
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Amount of transactions with related party during the financial reporting period.

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

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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

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