Name:	snh_EquityMethodInvestmentPropertyInsuranceAnnualPremiumAmount
Namespace Prefix:	snh_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Number of Buildings Covered by Property Insurance

No definition available.

Name:	snh_NumberofBuildingsCoveredbyPropertyInsurance
Namespace Prefix:	snh_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Represents the term of property insurance policy.

No definition available.

Name:	snh_PropertyInsuranceProgramTerm
Namespace Prefix:	snh_
Data Type:	xbrli:durationItemType
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Represents the number of shares purchased, from related party.

No definition available.

Name:	snh_RelatedPartyTransactionSharesPurchased
Namespace Prefix:	snh_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

Reference 1: 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 2: 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

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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.

No definition available.

Name:	us-gaap_RelatedPartyTransactionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
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Name:	us-gaap_BusinessAcquisitionAxis=snh_ReitManagementAndResearchIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
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Name:	us-gaap_EquityInterestIssuedOrIssuableByTypeAxis=us-gaap_CommonClassAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=snh_AffiliatesInsuranceCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: