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.

No definition available.

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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770

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- Definition

Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-Paragraph 2
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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- Definition

Amount of paid and unpaid cash dividends declared for award under share-based payment arrangement.

+ References

No definition available.

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Shareholders’ Equity - Distributions (Details) - USD ($) $ / shares in Units, $ in Thousands														12 Months Ended
	Nov. 19, 2020	Aug. 20, 2020	May 21, 2020	Feb. 20, 2020	Nov. 14, 2019	Aug. 15, 2019	May 16, 2019	Feb. 21, 2019	Nov. 15, 2018	Aug. 16, 2018	May 17, 2018	Feb. 22, 2018	Nov. 16, 2017	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Class of Stock [Line Items]
Common stock shares outstanding (in shares)														15,000,000	15,000,000
Common class A and B1
Class of Stock [Line Items]
Dividends paid (in dollars per share)														$ 1.52	$ 1.40	$ 1.00
Value of dividends														$ 24,789	$ 22,727	$ 16,169
Class A common shares
Class of Stock [Line Items]
Common stock shares outstanding (in shares)														15,395,641	15,302,710
ABP Trust \| Class A common shares
Class of Stock [Line Items]
Value of dividends		$ 4,500	$ 4,500	$ 4,500	$ 4,500	$ 4,500	$ 4,500	$ 4,500	$ 4,500	$ 3,750	$ 3,750	$ 3,750	$ 3,750	$ 18,000	$ 18,000	15,000
Common stock shares outstanding (in shares)														15,000,000
Subsequent Event \| Common class A and B1
Class of Stock [Line Items]
Dividends paid (in dollars per share)	$ 0.38
Value of dividends	$ 6,230
Common stock shares outstanding (in shares)	16,395,641
Subsequent Event \| ABP Trust \| Class A common shares
Class of Stock [Line Items]
Value of dividends	$ 4,500
RMR LLC \| Common class A and B1
Class of Stock [Line Items]
Value of dividends		$ 4,895	$ 4,894	$ 4,890	$ 4,891	$ 4,871	$ 4,872	$ 4,869	$ 4,869	$ 4,044	$ 4,044	$ 4,040	$ 4,041	$ 19,570	$ 19,481	$ 16,169
RMR LLC \| RMR LLC
Class of Stock [Line Items]
Dividends paid (in dollars per share)		$ 0.30	$ 0.30	$ 0.30	$ 0.30	$ 0.30	$ 0.30	$ 0.30	$ 0.30	$ 0.25	$ 0.25	$ 0.25	$ 0.25	$ 1.20	$ 1.20	$ 1.00
Value of dividends		$ 9,395	$ 9,394	$ 9,390	$ 9,391	$ 9,371	$ 9,372	$ 9,369	$ 9,369	$ 7,794	$ 7,794	$ 7,790	$ 7,791	$ 37,570	$ 37,481	$ 31,169
RMR LLC \| RMR LLC \| Common class A and B1
Class of Stock [Line Items]
Dividends paid (in dollars per share)		$ 0.38	$ 0.38	$ 0.38	$ 0.38	$ 0.35	$ 0.35	$ 0.35	$ 0.35	$ 0.25	$ 0.25	$ 0.25	$ 0.25
Value of dividends		$ 6,200	$ 6,200	$ 6,194	$ 6,195	$ 5,683	$ 5,684	$ 5,680	$ 5,680	$ 4,044	$ 4,044	$ 4,040	$ 4,041
RMR LLC \| Subsequent Event \| Common class A and B1
Class of Stock [Line Items]
Dividends paid (in dollars per share)	$ 0.30
Value of dividends	$ 4,919
RMR LLC \| Subsequent Event \| RMR LLC
Class of Stock [Line Items]
Value of dividends	$ 9,419