Represents the aggregate incentive business management fees.

No definition available.

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- Definition

Equity Method Investment, Number of Shares Owned

+ References

No definition available.

+ Details

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- Definition

Represents the amount of incentive fee revenue allocated to related party.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-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=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

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- Definition

This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(12))
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(10))
-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66022249&loc=d3e33749-111570

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(13)(f))
-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

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

No definition available.

+ Details

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Data Type:	xbrli:stringItemType
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- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=rmr_AbpTrustMember
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- Details

Name:	us-gaap_RelatedPartyTransactionAxis=rmr_UpCTransactionMember
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- Details

Name:	dei_LegalEntityAxis=rmr_ABPTrust1Member
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- Details

Name:	us-gaap_EquityInterestIssuedOrIssuableByTypeAxis=us-gaap_CommonClassAMember
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Balance Type:
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- Details

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- Details

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- Details

Name:	dei_LegalEntityAxis=rmr_AdamPortnoyMember
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Related Party Transactions - Additional Information (Details) - USD ($)		3 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2015	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014	May 19, 2016	Dec. 14, 2015	Jun. 05, 2015
Related Party Transaction [Line Items]
Equity in earnings of investee			$ 0	$ 115,000	$ 160,000
Incentive fee allocable to ABP Trust			26,611,000	0
Managed REITs
Related Party Transaction [Line Items]
Aggregate incentive business management fees	$ 62,263,000		$ 62,263,000	0	3,663,000
ABP Trust \| Up C Transaction
Related Party Transaction [Line Items]
Incentive fee allocable to ABP Trust		$ 26,611,000
ABP Trust \| Class A common shares
Related Party Transaction [Line Items]
Common stock shares outstanding							90,564	90,564
ABP Trust \| Class A units
Related Party Transaction [Line Items]
Common stock shares outstanding								15,000,000
AIC
Related Party Transaction [Line Items]
Equity in earnings of investee				$ 115,000	$ 160,000
AIC \| ABP Trust
Related Party Transaction [Line Items]
Ownership percentage by noncontrolling owners								14.30%
Class A common shares
Related Party Transaction [Line Items]
Common stock shares outstanding			15,082,432	15,000,000
Class A common shares \| Managed REITs \| Up C Transaction
Related Party Transaction [Line Items]
Common stock shares outstanding								15,000,000
Class A common shares \| ABP Trust
Related Party Transaction [Line Items]
Common stock shares outstanding						15,000,000
Class A common shares \| Adam Portnoy
Related Party Transaction [Line Items]
Number of shares owned (in shares)			20,438
Class A common shares \| Barry Portnoy
Related Party Transaction [Line Items]
Number of shares owned (in shares)			29,783