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

No definition available.

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

- 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 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

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Data Type:	num:areaItemType
Balance Type:	na
Period Type:	instant

- 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

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

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Namespace Prefix:
Data Type:	na
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- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
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Balance Type:
Period Type:

- Details

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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

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Namespace Prefix:
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Real Estate Properties (Acquisitions) (Details) - Acquisition ft² in Thousands, $ in Thousands			6 Months Ended
	Jul. 12, 2017 USD ($) ft² building property	Jan. 17, 2017 USD ($) ft² building property	Jul. 12, 2017 USD ($) ft² building property
Real Estate Properties
Weighted average amortization period			7 years 9 months 18 days
MOBs
Real Estate Properties
Number of properties \| property			2
Number of buildings acquired \| building			2
Area of real estate properties (in square feet) \| ft²	176		176
Purchase price including closing costs and working capital adjustments			$ 31,707
Real estate properties acquired, intangible lease assets	$ 10,275		$ 10,275
Kansas \| MOBs
Real Estate Properties
Number of properties \| property		1
Number of buildings acquired \| building		1
Area of real estate properties (in square feet) \| ft²		117
Purchase price including closing costs and working capital adjustments		$ 15,106
Real estate properties acquired, intangible lease assets		6,338
Maryland \| MOBs
Real Estate Properties
Number of properties \| property	1
Number of buildings acquired \| building	1
Area of real estate properties (in square feet) \| ft²	59		59
Purchase price including closing costs and working capital adjustments	$ 16,601
Real estate properties acquired, intangible lease assets	3,937		$ 3,937
Land \| MOBs
Real Estate Properties
Real estate properties acquired, property plant and equipment			7,660
Land \| Kansas \| MOBs
Real Estate Properties
Real estate properties acquired, property plant and equipment		1,522
Land \| Maryland \| MOBs
Real Estate Properties
Real estate properties acquired, property plant and equipment	6,138
Building improvements \| MOBs
Real Estate Properties
Real estate properties acquired, property plant and equipment			$ 13,772
Building improvements \| Kansas \| MOBs
Real Estate Properties
Real estate properties acquired, property plant and equipment		$ 7,246
Building improvements \| Maryland \| MOBs
Real Estate Properties
Real estate properties acquired, property plant and equipment	$ 6,526