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Weighted average interest rate on debt during the period.

No definition available.

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Represents the interest expense and other associated costs related to debt instrument during the period.

No definition available.

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Represents the option to increase borrowings on the credit facility.

No definition available.

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Represents the number of buildings serving as collateral for debt as of the balance sheet date.

No definition available.

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Represents the number of communities.

No definition available.

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Represents the number of public issues of unsecured senior notes.

No definition available.

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The number of real estate properties serving as collateral for debt as of the balance sheet date.

No definition available.

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sss

No definition available.

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Short-Term financing which is expected to be paid back relatively quickly, such as by a subsequent longer-term loan. Also called swing loan or bridge financing.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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The number of units (items of property) under capital lease arrangements.

No definition available.

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Percentage points added to the reference rate to compute the variable rate on the debt instrument.

No definition available.

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Face (par) amount of debt instrument at time of issuance.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Contractual interest rate for funds borrowed, under the debt agreement.

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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.

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Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

No definition available.

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The effective interest rate at the end of the reporting period.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

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The cash inflow from additional borrowings, net of cash paid to third parties in connection with debt origination.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt.

No definition available.

Name:	us-gaap_ProceedsFromIssuanceOfDebt
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Amount of real estate investment property, net of accumulated depreciation, which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; and (7) other real estate investments.

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The cash outflow to repay long-term debt that is wholly or partially secured by collateral. Excludes repayments of tax exempt secured debt.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

Name:	us-gaap_SecuredDebt
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Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Name:	us-gaap_SeniorNotes
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Name:	us-gaap_DebtInstrumentAxis=snh_SeniorUnsecuredNotesDue2024Member
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Name:	us-gaap_DebtInstrumentAxis=us-gaap_MortgagesMember
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Data Type:	na
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Data Type:	na
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Name:	us-gaap_DebtInstrumentAxis=us-gaap_UnsecuredDebtMember
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Data Type:	na
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Namespace Prefix:
Data Type:	na
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Name:	us-gaap_DebtInstrumentAxis=snh_TermLoanDue2022Member
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Data Type:	na
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Name:	us-gaap_DebtInstrumentAxis=snh_UnsecuredDebtSeptember2015Member
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Data Type:	na
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