Name:	dhc_CashPaidPlusAssumedDebtExcludingClosingCostsPlusOtherSettlementAdjustments
Namespace Prefix:	dhc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Represents the increase or decrease on the annual rent the lessee is obligated to pay on an operating lease.

No definition available.

Name:	dhc_IncreaseDecreaseOperatingLeasesAnnualRent
Namespace Prefix:	dhc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Amount of committed but unspent tenant related obligations based on executed lease.

No definition available.

Name:	dhc_LeaseCommittedButUnspentTenantRelatedObligations
Namespace Prefix:	dhc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Represents the amount of expenditure committed by entity relating to leases.

No definition available.

Name:	dhc_LeasesCommittedExpenditure
Namespace Prefix:	dhc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

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

No definition available.

Name:	dhc_NumberOfPropertiesAcquired
Namespace Prefix:	dhc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Number of Real Estate Properties Closed

No definition available.

Name:	dhc_NumberOfRealEstatePropertiesClosed
Namespace Prefix:	dhc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Represents the aggregate purchase price excluding acquisition costs of real estate properties acquired or agreed to be acquired by the entity.

No definition available.

Name:	dhc_RealEstateAggregatePurchasePrice
Namespace Prefix:	dhc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

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

No definition available.

Name:	dhc_RealEstateAggregateSalesPrice
Namespace Prefix:	dhc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Represents the amount of improvements to real estate properties made by lessees and purchased by the entity.

No definition available.

Name:	dhc_RealEstateImprovementsByLesseePurchased
Namespace Prefix:	dhc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Related Party Transaction, Amount Of Improvements To Communities To Leased Asset

No definition available.

Name:	dhc_RelatedPartyTransactionAmountOfImprovementsToCommunitiesToLeasedAsset
Namespace Prefix:	dhc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Represents the area of the real estate property subject to an operating lease.

No definition available.

Name:	dhc_SquareFootageOfRealEstatePropertyLeased
Namespace Prefix:	dhc_
Data Type:	num:areaItemType
Balance Type:	na
Period Type:	duration

Area of a real estate property.

No definition available.

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

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.

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

The difference between the carrying value and the sale price of real estate or properties that were intended to be sold or held for capital appreciation or rental income. This element refers to the gain (loss) included in earnings and not to the cash proceeds of the sale. This element is a noncash adjustment to net income when calculating net cash generated by operating activities using the indirect method.

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Name:	us-gaap_GainLossOnSaleOfProperties
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of cash paid for interest capitalized, classified as investing activity.

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Name:	us-gaap_InterestPaidCapitalized
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

The cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets.

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

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

The cumulative amount of depreciation for real estate property held for investment purposes.

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Name:	us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

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

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

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

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

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

Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=dhc_MedicalOfficeBuildingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=dhc_SeniorLivingCommunityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_StatementGeographicalAxis=dhc_CaliforniaColoradoAndOregonMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=dhc_FiveStarQualityCareIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=dhc_WelnessCenterMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=dhc_LifeScienceBuildingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=dhc_MedicalOfficeBuildingandLifeScienceBuildingMember
Namespace Prefix:
Data Type:	na
Balance Type:
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Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=dhc_SeniorLivingCommunitiesIndependentLivingAssistedLivingandSkilledNursingFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
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Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=dhc_LandParcelMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_StatementGeographicalAxis=stpr_AZ
Namespace Prefix:
Data Type:	na
Balance Type:
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Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=dhc_VacatedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_StatementGeographicalAxis=stpr_CA
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=dhc_FiveStarQualityCareIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
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Name:	us-gaap_DisposalGroupClassificationAxis=us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

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