Represents the area of a real estate property, held for sale.

No definition available.

Name:	snh_AreaOfRealEstatePropertyHeldForSale
Namespace Prefix:	snh_
Data Type:	num:areaItemType
Balance Type:	na
Period Type:	instant

- Definition

The number of buildings owned by the entity, which are classified as held for sale as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	snh_NumberOfBuildingsHeldForSale
Namespace Prefix:	snh_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the number of communities.

+ References

No definition available.

+ Details

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

- Definition

Represents the number of tenants.

+ References

No definition available.

+ Details

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

- Definition

Amount of cash received from agreement relating to settlement, termination of lease and transfer operations.

+ References

No definition available.

+ Details

Name:	snh_ProceedsFromSettlementAgreement
Namespace Prefix:	snh_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

This element represents the aggregate sales price excluding closing costs, of real estate properties sold by the entity during the period.

+ References

No definition available.

+ Details

Name:	snh_RealEstateAggregateSalesPrice
Namespace Prefix:	snh_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=51824106&loc=d3e2420-110228

Reference 2: 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=56944662&loc=d3e3602-108585

+ Details

Name:	us-gaap_AssetImpairmentCharges
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The number of units in a real estate property owned as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfUnitsInRealEstateProperty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Carrying amount as of the balance sheet date of investments in land and buildings held for sale, excluding real estate considered to be inventory of the entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1(f))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

Name:	us-gaap_RealEstateHeldforsale
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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

Name:	us-gaap_RealEstatePropertiesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_OtherAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DisposalGroupClassificationAxis=us-gaap_DiscontinuedOperationsHeldforsaleMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	snh_OperatingLeasesOfLessorLesseeAxis=snh_TaxableREITSubsidiariesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=snh_TripleNetSeniorLivingCommunitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=snh_MedicalOfficeBuildingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=snh_MedicalOfficeBuildingAndLandParcelMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=snh_SeniorLivingCommunityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DisposalGroupClassificationAxis=us-gaap_DiscontinuedOperationsDisposedOfBySaleMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=snh_LandParcelMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Real Estate Properties - Discontinued Operations and Properties Held for Sale (Details) $ in Thousands	1 Months Ended				3 Months Ended
	Apr. 30, 2016 USD ($) item	Mar. 31, 2016 USD ($) ft² item building	Feb. 29, 2016 USD ($)	Feb. 28, 2015 USD ($) property	Mar. 31, 2016 USD ($) ft² item building community
Real estate properties
Impairment of assets					$ 7,390
Number of tenants \| item	1
Other assets \| Discontinued Operations, Held-for-sale
Real estate properties
Assets held for sale		$ 7,125			7,125
Five Star \| TRS
Real estate properties
Proceeds from settlement agreement	$ 2,365
Triple Net Leased Senior Living Communities
Real estate properties
Impairment of assets					$ 4,391
Number of communities \| community					2
Number of tenants \| item					2
MOBs
Real estate properties
Number of Buildings Held For Sale \| building		1			1
MOBs \| Discontinued Operations, Held-for-sale
Real estate properties
Number of Buildings Held For Sale \| item		1			1
Area Of Real Estate Property Held For Sale \| ft²		65,000			65,000
MOB and land parcel
Real estate properties
Impairment of assets					$ 2,999
Senior Living Communities \| Discontinued Operations, Disposed of by Sale
Real estate properties
Number of communities \| property				1
Sale price of property sold and agreed to be sold				$ 250
Senior Living Communities \| Discontinued Operations, Held-for-sale
Real estate properties
Number of communities \| community					1
Number of living units \| item		140			140
Sale price of property sold and agreed to be sold			$ 9,500
Land parcel \| Discontinued Operations, Disposed of by Sale
Real estate properties
Sale price of property sold and agreed to be sold		$ 700