The aggregate market value of shares newly issued during the reporting period under the plan.

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Represents the closing share price of unvested shares.

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The number of unvested shares, that will vest in four years.

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The number of unvested shares, that will vest in next fiscal year.

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The number of unvested shares, that will vest in three years.

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The number of unvested shares, that will vest in two years.

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Represents the market value of shares, newly issued during the reporting period under the plan, to each individual.

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No definition available.

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Represents the number of trustees who have been granted shares under equity compensation plan.

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Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Unrecognized cost of unvested share-based compensation awards.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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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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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Number of share instruments newly issued under a share-based compensation plan.

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Shareholders' Equity - Share Award Plans (Details)	1 Months Ended			12 Months Ended
Shareholders' Equity - Share Award Plans (Details)	May 31, 2016 USD ($) trustee shares	Sep. 30, 2015 USD ($) shares	May 31, 2015 USD ($) trustee shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($) trustee $ / shares shares
Share award plans
Number of trustees \| trustee	5		5			5
Share-based compensation expense \| $				$ 2,195,000	$ 1,373,000	$ 1,914,000
Share Award Plans
Share award plans
Remaining common shares available for issuance				2,567,616
Estimated future compensation for the unvested shares \| $				$ 2,904,000
Closing share price (in dollars per share) \| $ / shares				$ 18.93
Weighted average period over which the compensation expense will be recorded				1 year 8 months 12 days
Number of Shares
Unvested shares at the beginning of the year				158,874	153,478	150,711
Shares granted				92,150	99,000	94,200
Shares vested				(97,614)	(93,604)	(91,433)
Unvested shares at the end of the year				153,410	158,874	153,478
Weighted Average Grant Date Fair Value
Unvested shares at the beginning of the year (in dollars per share) \| $ / shares				$ 19.39	$ 23.39	$ 23.84
Shares granted (in dollars per share) \| $ / shares				21.18	16.30	21.83
Shares vested (in dollars per share) \| $ / shares				21.09	16.17	21.87
Unvested shares at the end of the year (in dollars per share) \| $ / shares				$ 19.92	$ 19.39	$ 23.39
Scheduled to vest unvested shares
2017				60,040
2018				46,050
2019				31,390
2020				15,930
Share Award Plans \| Trustees
Share award plans
Common shares awarded	2,500	2,500	2,500			2,500
Aggregate market value of shares awarded \| $		$ 41,000				$ 306,000
Market value of shares awarded to each Trustee \| $						$ 61,000
Share Award Plans \| RMR LLC \| Officers and Employees
Share award plans
Common shares awarded				79,650	84,000	81,700
Aggregate market value of shares awarded \| $	$ 228,000		$ 252,000	$ 1,724,000	$ 1,321,000	$ 1,750,000
Market value of shares awarded to each Trustee \| $	$ 46,000		$ 50,000
Award vesting period				5 years