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Number of shares of equity interests issued or issuable to acquire entity.

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Aggregate dividends paid during the period for each share of common stock outstanding.

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Amount of paid and unpaid cash, stock, and paid-in-kind (PIK) dividends declared, for example, but not limited to, common and preferred stock.

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Carrying value as of the balance sheet date of dividends declared but unpaid on equity securities issued by the entity and outstanding.

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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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Amount of cash outflow in the form of ordinary dividends to common shareholders of the parent entity.

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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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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 - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended						12 Months Ended
	Feb. 22, 2018	Jan. 31, 2018	May 31, 2017	May 31, 2016	Dec. 31, 2015	Sep. 30, 2015	May 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jan. 19, 2018	Dec. 31, 2014
Scheduled to vest unvested shares
Share-based compensation expense								$ 2,155	$ 2,195	$ 1,373
Distribution to common shareholders (in dollars per share)								$ 1.56	$ 1.56	$ 1.56
Distribution to common shareholders								$ 370,608	$ 370,489	$ 356,390
Dividends paid in kind per share					$ 0.1320
Common stock dividends, ordinary income distribution percentage								88.44%	58.77%	51.48%
Common stock dividends, capital distribution percentage								0.00%	40.67%	47.80%
Common stock dividends, qualified distribution percentage								0.71%	0.56%	0.72%
Common stock dividends, capital gain distribution percentage								10.85%	0.00%	0.00%
RMR LLC
Scheduled to vest unvested shares
Shares issued in connection with acquisition										81,557
Distribution to common shareholders					$ 2,635
Distribution ratio, RMR Inc shares per common shares					0.0111
Certain Our Officers And Employees Of RMR LLC
Scheduled to vest unvested shares
Shares purchased from certain of our officers and other employees of RMR LLC								17,170	19,230
Share Award Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining common shares available for issuance								2,481,686
Number of unvested shares					158,874			148,010	153,410	158,874		153,478
Scheduled to vest unvested shares
2018								57,250
2019								44,230
2020								30,410
2021								16,120
Estimated future compensation for the unvested shares								$ 2,834
Closing share price (in dollars per share)								$ 19.15
Weighted average period over which the compensation expense will be recorded								1 year 8 months 12 days
Share Award Plans \| Trustees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common shares awarded			3,000	2,500		2,500	2,500
Aggregate market value of shares awarded						$ 41
Share Award Plans \| RMR LLC \| Officers and Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate market value of shares awarded			$ 319	$ 228			$ 252
Market value of shares awarded to each Trustee			$ 64	$ 46			$ 50
Award vesting period								5 years
Subsequent Event
Scheduled to vest unvested shares
Repurchase of common shares (in shares)		4,628
Share price (in dollars per share)		$ 19.15
Distribution to common shareholders (in dollars per share)	$ 0.39
Distribution declared to common shareholders (in dollars per share)											$ 0.39
Distribution declared to common shareholders											$ 92,676
Dividends	$ 92,642