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Amount of distribution received from equity method investee for return on investment, classified as operating activities. Excludes distribution for return of investment, classified as investing activities.

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Amount of income (loss) for proportionate share of equity method investee's income (loss).

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Amount of increase (decrease) in other comprehensive income, after tax, from changes classified as other.

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The percentage charged for managing real estate properties.

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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.

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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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Cash received on stock transaction after deduction of issuance costs.

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The number of shares issued or sold by the subsidiary or equity method investee per stock transaction.

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Per share amount received by subsidiary or equity investee for each share of common stock issued or sold in the stock transaction.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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Percentage of vesting of award under share-based payment arrangement.

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Related Person Transactions (Details) $ / shares in Units, $ in Thousands				6 Months Ended			12 Months Ended
	Feb. 13, 2020 USD ($)	Jul. 01, 2019 USD ($) $ / shares shares	Aug. 03, 2017 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2019 USD ($) agreement	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Related Party Transaction [Line Items]
Sale of stock, consideration received on transaction			$ 493,866
Equity in net losses of investees							$ (1,259)	$ (2,269)	$ (13)
Distribution of earnings from Affiliates Insurance Company							2,438	0	0
Property Insurance Premium Expense
Related Party Transaction [Line Items]
Related party transaction							$ 190	198	91
RMR LLC
Related Party Transaction [Line Items]
Number of agreements with RMR LLC to provide management services \| agreement							2
Rental income earned							$ 1,142	1,026	303
Related party transaction								16,381	12,464
AIC
Related Party Transaction [Line Items]
Amount invested in equity investee							298	8,751	8,304
Equity in unrealized gain (loss) of investees							281	516	608
Equity in net losses of investees							90	$ (69)	$ 461
AIC \| Subsequent Event
Related Party Transaction [Line Items]
Distribution of earnings from Affiliates Insurance Company	$ 9,000
AIC \| Property Insurance Premium Expense, June 2018
Related Party Transaction [Line Items]
Related party transaction					$ 757
AIC \| Property Insurance Premium Expense, June 2017
Related Party Transaction [Line Items]
Related party transaction						$ 1,032
AIC \| Property Insurance Premium Expense, June 2019
Related Party Transaction [Line Items]
Related party transaction				$ 1,211
IPO \| RMR Inc
Related Party Transaction [Line Items]
Number of shares sold (in shares) \| shares		2,801,060
Sale of stock (in dollars per share) \| $ / shares		$ 40.00
Sale of stock, consideration received on transaction		$ 104,674
SIR \| AIC \| Property Insurance Premium Expense, June 2019
Related Party Transaction [Line Items]
Related party transaction							$ 1,666
AIC \| RMR LLC
Related Party Transaction [Line Items]
Service fee percentage							3.00%
Officers and Other Employees \| Common Shares \| 2009 Award Plan
Related Party Transaction [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period							4 years
Officers and Other Employees \| Share-based Payment Arrangement, Tranche 1 \| Common Shares \| 2009 Award Plan
Related Party Transaction [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage							20.00%
Officers and Other Employees \| Share-based Payment Arrangement, Tranche 2 \| Common Shares \| 2009 Award Plan
Related Party Transaction [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage							20.00%
Officers and Other Employees \| Share-based Payment Arrangement, Tranche 3 \| Common Shares \| 2009 Award Plan
Related Party Transaction [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage							20.00%
Officers and Other Employees \| Share-based Compensation Award, Tranche 4 \| Common Shares \| 2009 Award Plan
Related Party Transaction [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage							20.00%
Officers and Other Employees \| Share-based Compensation Award, Tranche 5 \| Common Shares \| 2009 Award Plan
Related Party Transaction [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage							20.00%