Acquisition Costs Incurred

No definition available.

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

- Definition

Cash Paid plus Assumed Debt, including closing costs plus other settlement adjustments

+ References

No definition available.

+ Details

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

- Definition

The amount of premium on assumed debt that an Entity assumes in acquiring a business or in consideration for an asset received in a noncash (or part noncash) acquisition.

+ References

No definition available.

+ Details

Name:	snh_NoncashOrPartNoncashAcquisitionPremiumOnDebtAssumed1
Namespace Prefix:	snh_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

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

- Definition

Represents the number of buildings acquired or agreed to be acquired by the entity.

+ References

No definition available.

+ Details

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

- Definition

Represents the number of properties acquired or agreed to be acquired by the entity.

+ References

No definition available.

+ Details

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

- Definition

Represents the intangible lease assets recorded as part of the real estate acquisition.

+ References

No definition available.

+ Details

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

- Definition

Represents the intangible lease liabilities recorded as part of the real estate acquisition.

+ References

No definition available.

+ Details

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

- Definition

Represents the property plant and equipment assets recorded as part of the real estate acquisition.

+ References

No definition available.

+ Details

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

- Definition

Area of a real estate property.

+ References

No definition available.

+ Details

Name:	us-gaap_AreaOfRealEstateProperty
Namespace Prefix:	us-gaap_
Data Type:	num:areaItemType
Balance Type:	na
Period Type:	instant

- 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=68055307&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=66902209&loc=d3e3602-108585

+ Details

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

- Definition

Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_FiniteLivedIntangibleAssetUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of debt that an Entity assumes in acquiring a business or in consideration for an asset received in a noncash (or part noncash) acquisition. Noncash is defined as transactions during a period that affect recognized assets or liabilities but that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4332-108586

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4313-108586

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4304-108586

+ Details

Name:	us-gaap_NoncashOrPartNoncashAcquisitionDebtAssumed1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

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

- Definition

The number of states the entity operates in as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfStatesInWhichEntityOperates
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
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_PropertyPlantAndEquipmentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementGeographicalAxis=stpr_KS
Namespace Prefix:
Data Type:	na
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Period Type:

- Details

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

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_LandMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_BuildingImprovementsMember
Namespace Prefix:
Data Type:	na
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Period Type:

Real Estate Properties (Details) ft² in Thousands, $ in Thousands	1 Months Ended					3 Months Ended
	Jan. 31, 2017 USD ($) ft²	Jan. 31, 2017 USD ($) ft² living_unit	Jan. 31, 2017 USD ($) ft² building	Jan. 31, 2017 USD ($) ft²	Jan. 31, 2017 USD ($) ft² property	Mar. 31, 2017 USD ($) state building property	Mar. 31, 2016 USD ($)
Real Estate Properties
Number of properties owned \| property						434
Number of buildings owned \| building						460
Number of states in which properties are located \| state						42
Impairment of assets						$ 0	$ 7,390
Acquisition
Real Estate Properties
Weighted average amortization period	10 years 3 months 18 days
Kansas \| Acquisition \| MOBs
Real Estate Properties
Number of properties		1			1
Number of buildings acquired \| building			1
Area of real estate properties (in square feet) \| ft²	117	117	117	117	117
Purchase price including closing costs and working capital adjustments				$ 15,106
Acquisition and certain other transaction related costs				35
Real estate properties, acquired intangible lease assets	$ 6,338	$ 6,338	$ 6,338	6,338	$ 6,338
Real estate properties acquired, intangible lease liabilities	$ 0	$ 0	$ 0	0	$ 0
Assumption of mortgage notes payable				0
Premium on assumed debt				0
Kansas \| Land \| Acquisition \| MOBs
Real Estate Properties
Real estate properties acquired, property plant and equipment				1,522
Kansas \| Building improvements \| Acquisition \| MOBs
Real Estate Properties
Real estate properties acquired, property plant and equipment				$ 7,246