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

Represents the number shares acquired which have been accounted under cost method of accounting.

No definition available.

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

The initial other liabilities recorded which is the difference of the total consideration paid and the fair market value of the investment.

No definition available.

Name:	snh_InitialOtherLiabilities
Namespace Prefix:	snh_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Represents the number of consecutive months used for average annual base management fees and internal audit services expense.

No definition available.

Name:	snh_NumberConsecutiveMonthsForAverageFeesAndExpenses
Namespace Prefix:	snh_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents the number of management agreements the company would need to terminate for convenience before a termination fee is incurred.

No definition available.

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

presents the number of management agreements RMR LLC would need to terminate for good cause before a termination fee is incurred.

No definition available.

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

Represents the number of management agreements the company would need to terminate for a performance reason before a termination fee is incurred.

No definition available.

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

Number of months prior to the effective date of the nonrenewal termination used to calculate the property management termination fee.

No definition available.

Name:	snh_NumberOfMonthsUsedToCalculatePropertyManagementTerminationFee
Namespace Prefix:	snh_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents the base management fee payable as a percentage of historical cost of other real estate investments, excluding transferred assets for investments after specified amount.

No definition available.

Name:	snh_RelatedPartyTransactionBaseBusinessManagementFeePayableAsPercentageOfHistoricalCostOfOtherRealEstateInvestmentsExcludingTransferredAssetsForInvestmentsAfterTheSpecifiedAmount
Namespace Prefix:	snh_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Represents the base management fees payable as a percentage of aggregate book value of real estate assets or transferred assets.

No definition available.

Name:	snh_RelatedPartyTransactionBaseManagementFeePayableAsPercentageOfAggregateBookValueOfRealEstateAssetsOrTransferredAssets
Namespace Prefix:	snh_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Represents the base management fee payable as a percentage of average closing price per share of common shares on NYSE.

No definition available.

Name:	snh_RelatedPartyTransactionBaseManagementFeePayableAsPercentageOfAverageClosingStockPriceOnStockExchange
Namespace Prefix:	snh_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Represents the base management fees payable as a percentage of average historical cost of real estate investments, excluding transferred assets for investments exceeding specified amount.

No definition available.

Name:	snh_RelatedPartyTransactionBaseManagementFeePayableAsPercentageOfAverageHistoricalCostOfRealEstateInvestmentsExcludingTransferredAssetsForInvestmentsExceedingSpecifiedAmount
Namespace Prefix:	snh_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Represents the base management fees payable as a percentage of average historical cost of real estate investments, excluding transferred assets for investments up to specified amount.

No definition available.

Name:	snh_RelatedPartyTransactionBaseManagementFeePayableAsPercentageOfAverageHistoricalCostOfRealEstateInvestmentsExcludingTransferredAssetsForInvestmentsUpToSpecifiedAmount
Namespace Prefix:	snh_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Represents the base management fee payable as a percentage of average market capitalization exceeding specified amount.

No definition available.

Name:	snh_RelatedPartyTransactionBaseManagementFeePayableAsPercentageOfAverageMarketCapitalizationExceedingSpecifiedAmount
Namespace Prefix:	snh_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Represents the amount of average market capitalization for payment of base management fee.

No definition available.

Name:	snh_RelatedPartyTransactionBaseManagementFeePayableAverageMarketCapitalization
Namespace Prefix:	snh_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Represents the threshold amount of average market capitalization for payment of the base management fee.

No definition available.

Name:	snh_RelatedPartyTransactionBaseManagementFeePayableThresholdAmountOfAverageMarketCapitalization
Namespace Prefix:	snh_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Represents the threshold amount of other real estate investments for payment of base management fee.

No definition available.

Name:	snh_RelatedPartyTransactionBaseManagementFeePayableThresholdAmountOfOtherRealEstateInvestments
Namespace Prefix:	snh_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Represents the threshold amount of real estate investments for payment of base management fee.

No definition available.

Name:	snh_RelatedPartyTransactionBaseManagementFeePayableThresholdAmountOfRealEstateInvestments
Namespace Prefix:	snh_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Represents the cap on the value of the incentive fee payable per share of our total shares outstanding.

No definition available.

Name:	snh_RelatedPartyTransactionIncentiveFeePerShareMaximum
Namespace Prefix:	snh_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

Represents the window or numbers of business days after any calendar year to provide notice for termination of property management agreement by the related party for performance reasons.

No definition available.

Name:	snh_RelatedPartyTransactionNumberOfBusinessDayWindowAfterEndOfAnyCalendarYearPriorWrittenNoticeForTerminationOfPropertyManagementAgreementForPerformanceByRelatedParty
Namespace Prefix:	snh_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents the number of business days notice for termination of either agreement by related party, if the entity undergoes a change of control.

No definition available.

Name:	snh_RelatedPartyTransactionNumberOfBusinessDaysNoticeForTerminationOfEitherServiceAgreementByRelatedPartyPursuantToChangeOfControlInEntity
Namespace Prefix:	snh_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents the number of business days notice for termination of property management agreement by the related party for convenience.

No definition available.

Name:	snh_RelatedPartyTransactionNumberOfBusinessDaysPriorWrittenNoticeForTerminationOfPropertyManagementAgreementForConvenienceByRelatedParty
Namespace Prefix:	snh_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents the number of business days notice for termination of property management agreement by the related party for performance, provided within a given window or numbers of days after any calendar year.

No definition available.

Name:	snh_RelatedPartyTransactionNumberOfBusinessDaysPriorWrittenNoticeForTerminationOfPropertyManagementAgreementForPerformanceByRelatedParty
Namespace Prefix:	snh_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents the percentage of incentive fee payable.

No definition available.

Name:	snh_RelatedPartyTransactionPercentageOfIncentiveFeePayable
Namespace Prefix:	snh_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Represents the period of prior written notice for termination of the service agreements by the related party.

No definition available.

Name:	snh_RelatedPartyTransactionPeriodOfPriorWrittenNoticeForTerminationOfServiceAgreementsByRelatedParty
Namespace Prefix:	snh_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents the period of prior written notice for termination of the service agreements by the related party, before amendment.

No definition available.

Name:	snh_RelatedPartyTransactionPeriodOfPriorWrittenNoticeForTerminationOfServiceAgreementsByRelatedPartyBeforeAmendment
Namespace Prefix:	snh_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents the window after a change in control to provide notice for termination of property management agreement by the related party.

No definition available.

Name:	snh_RelatedPartyTransactionWindowAfterChangeOfControlPriorWrittenNoticeForTerminationOfPropertyManagementAgreementByRelatedParty
Namespace Prefix:	snh_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents the period over which the related party agrees to provide certain transition services following an applicable termination of the agreement.

No definition available.

Name:	snh_RelatedPartytransactionperiodoftransitionservicesprovidedByRelatedPartyAfterTerminationOfAgreement
Namespace Prefix:	snh_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents the period over which the discount on shares acquired is amortized in years.

No definition available.

Name:	snh_StaightLineDiscountAmortizationPeriod
Namespace Prefix:	snh_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents the factor used to calculate the termination fee applied against the annual base management fee and annual internal audit services expense.

No definition available.

Name:	snh_TerminationFeeFactor
Namespace Prefix:	snh_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

Represents the factor used to calculate the termination fee applied against the average monthly property management fee.

No definition available.

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

epresents the remaining term assumption in years used to calculate the fee for termination of one or both of the company's amended management agreements for a performance reason.

No definition available.

Name:	snh_TerminationFeeRemainingTermAssumption
Namespace Prefix:	snh_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents the term in years used to calculate the fee for termination of one or both of the company's amended management agreements for a performance reason.

No definition available.

Name:	snh_TerminationFeeTerm
Namespace Prefix:	snh_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Number of months prior to or following giving notice of termination or non-renewal of the business management agreement other than for cause, that the property management agreement can be renewed.

No definition available.

Name:	snh_Terminationofpropertymanagementagreementinrelationtobusinessmanagementagreementtermination
Namespace Prefix:	snh_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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Original amount of cost-method investments at the acquisition date.

No definition available.

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

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=snh_ReitManagementAndResearchLLCMember
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Name:	dei_LegalEntityAxis=snh_ReitManagementAndResearchIncMember
Namespace Prefix:
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Namespace Prefix:
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Namespace Prefix:
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Namespace Prefix:
Data Type:	na
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