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

Represents the number of buildings owned as of the balance sheet date.

No definition available.

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

Represents the number of communities.

No definition available.

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

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

No definition available.

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

Amount after tax of income (loss) from operations classified as a discontinued operation. Excludes gain (loss) on disposal and provision for gain (loss) until disposal.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 50

-Paragraph 5C

-Subparagraph (b)(2)

-URI http://asc.fasb.org/extlink&oid=51717284&loc=SL51721675-107760

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 45

-Paragraph 3A

-URI http://asc.fasb.org/extlink&oid=51716988&loc=SL51721523-107759

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 45

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=51716988&loc=d3e957-107759

Name:	us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationDuringPhaseOutPeriodNetOfTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of revenue attributable to disposal group, including, but not limited to, discontinued operation.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 50

-Paragraph 5B

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=51717284&loc=SL51721673-107760

Name:	us-gaap_DisposalGroupIncludingDiscontinuedOperationRevenue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The number of real estate properties owned as of the balance sheet date.

No definition available.

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

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

No definition available.

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

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.

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

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

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

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

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

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

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

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