Related Person Transactions - REITs, for which RMR LLC provides Management Services (Details) $ in Thousands	3 Months Ended
Mar. 31, 2017 USD ($) agreement shares	Dec. 31, 2016 USD ($)
SIR
Related Party Transaction [Line Items]
Shares holding (in shares)	24,918,421
Percentage of outstanding shares owned	27.90%
RMR Inc \| Class A common shares
Related Party Transaction [Line Items]
Shares holding (in shares)	1,214,225
RMR LLC
Related Party Transaction [Line Items]
Number of agreements \| agreement	2
AIC
Related Party Transaction [Line Items]
Carrying value of equity method investments \| $	$ 7,485	$ 7,235

Represents the number of agreements with RMR LLC to provide management services to the company.

No definition available.

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- Definition

This element represents the aggregate cost of investments accounted for under the equity method of accounting.

+ 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 210.5-02.12)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66011266&loc=d3e33918-111571

+ Details

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- 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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- Definition

Cumulative number of shares issued or sold by the subsidiary or equity method investee on all stock transactions.

+ References

No definition available.

+ Details

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Balance Type:	na
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- Details

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Namespace Prefix:
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- Details

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- Details

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- Details

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- Details

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