Aggregate Shares Issued

No definition available.

Name:	dhc_AggregateSharesIssued
Namespace Prefix:	dhc_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Consumer Price Index Annual Estimated Increase

+ References

No definition available.

+ Details

Name:	dhc_ConsumerPriceIndexAnnualEstimatedIncrease
Namespace Prefix:	dhc_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Number Of Communities Leased

+ References

No definition available.

+ Details

Name:	dhc_NumberOfCommunitiesLeased
Namespace Prefix:	dhc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the number of communities managed by a related party.

+ References

No definition available.

+ Details

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

- Definition

Number Of Leases With Related Party

+ References

No definition available.

+ Details

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

- Definition

Number of Real Estate Properties Inadequate Documentation

+ References

No definition available.

+ Details

Name:	dhc_NumberOfRealEstatePropertiesInadequateDocumentation
Namespace Prefix:	dhc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number Of Real Estate Properties Transitioned

+ References

No definition available.

+ Details

Name:	dhc_NumberOfRealEstatePropertiesTransitioned
Namespace Prefix:	dhc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Payments Made In Exchange For Customary Release

+ References

No definition available.

+ Details

Name:	dhc_PaymentsMadeInExchangeForCustomaryRelease
Namespace Prefix:	dhc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Penalties for Inadequate Documentation

+ References

No definition available.

+ Details

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

- Definition

Refunded Management Fees

+ References

No definition available.

+ Details

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

- Definition

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

+ References

No definition available.

+ Details

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

- Definition

Related Party Transaction, Business And Property Management Agreement, Number Of Extension Options

+ References

No definition available.

+ Details

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

- Definition

Related Party Transaction Capitalized Amount

+ References

No definition available.

+ Details

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

- Definition

Related Party Transaction, Construction Supervision Fee Percentage Of Construction Cost

+ References

No definition available.

+ Details

Name:	dhc_RelatedPartyTransactionConstructionSupervisionFeePercentageOfConstructionCost
Namespace Prefix:	dhc_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Expenses recognized during the period resulting from property management transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party during the period.

+ References

No definition available.

+ Details

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

- Definition

Related Party Transaction, Monthly Minimum Rent Payable

+ References

No definition available.

+ Details

Name:	dhc_RelatedPartyTransactionMonthlyMinimumRentPayable
Namespace Prefix:	dhc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Related Party Transaction, Percentage Target EBITDA Threshold For Contract Termination

+ References

No definition available.

+ Details

Name:	dhc_RelatedPartyTransactionPercentageTargetEBITDAThresholdForContractTermination
Namespace Prefix:	dhc_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Related Party Transaction, Percentage of Annual Incentive Fee

+ References

No definition available.

+ Details

Name:	dhc_RelatedPartyTransactionPercentageofAnnualIncentiveFee
Namespace Prefix:	dhc_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the management fees payable to related parties under property management agreement expressed as a percentage of gross revenues.

+ References

No definition available.

+ Details

Name:	dhc_RelatedPartyTransactionPropertyManagementAgreementManagementFeesAsPercentageOfGrossRevenues
Namespace Prefix:	dhc_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Related Party Transaction, Property Management Agreement, Management Fees As Percentage Of Gross Revenues Realized At All Communities

+ References

No definition available.

+ Details

Name:	dhc_RelatedPartyTransactionPropertyManagementAgreementManagementFeesAsPercentageOfGrossRevenuesRealizedAtAllCommunities
Namespace Prefix:	dhc_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Related Party Transaction, Property Management Agreement, Renewal Term

+ References

No definition available.

+ Details

Name:	dhc_RelatedPartyTransactionPropertyManagementAgreementRenewalTerm
Namespace Prefix:	dhc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the annual rent as a percentage of the entity's gross revenues.

+ References

No definition available.

+ Details

Name:	dhc_RelatedPartyTransactionTransactionAgreementAnnualRentAsAPercentageOfGrossRevenues
Namespace Prefix:	dhc_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Related Party Transaction, Transaction Agreement Annual Rent As A Percentage Of Gross Revenues, Amount

+ References

No definition available.

+ Details

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

- Definition

Related Party Transactions, Maximum Amount Of Contracts That Can Be Terminated Termination Percentage

+ References

No definition available.

+ Details

Name:	dhc_RelatedPartyTransactionsMaximumAmountOfContractsThatCanBeTerminatedTerminationPercentage
Namespace Prefix:	dhc_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Revenue Reserve, Inadequate Documentation

+ References

No definition available.

+ Details

Name:	dhc_RevenueReserveInadequateDocumentation
Namespace Prefix:	dhc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Trigger Basis For Capital Investments

+ References

No definition available.

+ Details

Name:	dhc_TriggerBasisForCapitalInvestments
Namespace Prefix:	dhc_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 23
-URI http://asc.fasb.org/extlink&oid=123586518&loc=d3e1043-128460

+ Details

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

- Definition

Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_CommonStockSharesIssued
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
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_ConcentrationRiskLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of gain (loss) on termination of lease before expiration of lease term.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 40
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=123386189&loc=SL77918607-209975

+ Details

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

- Definition

Amount of lease income from operating, direct financing, and sales-type leases. Includes, but is not limited to, variable lease payments, interest income, profit (loss) recognized at commencement, and lease payments paid and payable to lessor.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 30
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=124258985&loc=SL77919372-209981

+ Details

Name:	us-gaap_LeaseIncome
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 units in a real estate property owned as of the balance sheet date.

+ References

No definition available.

+ Details

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

- Definition

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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3213-108585

+ Details

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

- Definition

Amount of transactions with related party during the financial reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39603-107864

+ Details

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

- Definition

Expenses recognized resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

+ Details

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

- Details

Name:	dei_LegalEntityAxis=dhc_AlerisLifeIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=dhc_ThirdPartyInvestorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=srt_AffiliatedEntityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CounterpartyNameAxis=dhc_AlerisLifeIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_IncomeStatementLocationAxis=us-gaap_OperatingExpenseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=dhc_FiveStarQualityCareIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_DisposalGroupClassificationAxis=us-gaap_DisposalGroupDisposedOfByMeansOtherThanSaleNotDiscontinuedOperationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	srt_StatementScenarioAxis=us-gaap_ScenarioAdjustmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ProductOrServiceAxis=dhc_ResidentFeesAndServicesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=dhc_SeniorHousingOperatingPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Senior Living Community Leases and Management Agreements - Narrative (Details) $ in Thousands			1 Months Ended	12 Months Ended
	Jun. 09, 2021 USD ($) community unit	Apr. 01, 2019 USD ($)	Jan. 31, 2021 USD ($)	Dec. 31, 2021 USD ($) trustee option community property lease unit shares	Dec. 31, 2020 USD ($) property community shares	Dec. 31, 2019 USD ($) community property	Jan. 01, 2020 shares	Feb. 01, 2019 USD ($)
Concentration Risk
Common shares, shares issued (in shares) \| shares				238,994,894	238,268,478
Gain on lease termination				$ 0	$ 22,896	$ 0
Number of properties owned (property) \| property				390
Acquisition and certain other transaction related costs				$ 17,506	$ 814	$ 13,102
ALR
Concentration Risk
Common shares, shares issued (in shares) \| shares							10,268,158
Aggregate shares issued (shares) \| shares							16,118,849
Senior Living Communities
Concentration Risk
Number of properties owned (property) \| property					28	25
Number of units in real estate property \| unit				27,672
Five Star \| Minimum
Concentration Risk
Management fees as a percentage of gross revenues				5.00%
Construction supervision fee				3.00%
Property management agreement, management fees				70.00%
Five Star \| Maximum
Concentration Risk
Management fees as a percentage of gross revenues				6.00%
Construction supervision fee				5.00%
Property management agreement, management fees				80.00%
Five Star \| Investor \| Minimum
Concentration Risk
Percentage of annual incentive fee				15.00%
Five Star \| Investor \| Maximum
Concentration Risk
Percentage of annual incentive fee				25.00%
Affiliated Entity \| ALR
Concentration Risk
Number of communities managed \| community						78
Affiliated Entity \| Five Star
Concentration Risk
Number of communities leased by the company \| community						166
Amounts of transaction					$ 75,000	$ 137,898
Gain on lease termination					22,896
Monthly minimum rent payable								$ 11,000
Payments to acquire property, plant, and equipment						49,155
Management fees as a percentage of gross revenues				5.00%
Percentage of annual incentive fee				15.00%
Consumer price index annual estimated increase				2.00%
Trigger basis for capital investment ratio (percent)				6.00%
Business and property management agreement, number of agreements \| option				2
Renewal term (years)				5 years
Number of leases with related party \| lease				5
Amount of improvements to communities						111,603
Expenses from property management agreement transactions with related party				$ 47,479	62,880	$ 15,327
Related party transaction capitalized amount				3,615	2,467
Payments made in exchange for customary release			$ 5,763
Refunded management fees			$ 115
Lease income				1,591	1,561
Affiliated Entity \| Five Star \| Property Operating Expense
Concentration Risk
Expenses from property management agreement transactions with related party				$ 43,864	$ 60,413
Affiliated Entity \| Five Star \| Senior Living Communities
Concentration Risk
Number of communities managed \| community				120	235	78
Expenses from transactions with related party				$ 11,233	$ 25,687	$ 5,920
Number of real estate properties inadequate documentation \| trustee				1
Five Star \| Senior Living Communities
Concentration Risk
Number of properties owned (property) \| community	120
Related party transactions, termination percentage	10.00%
Percentage of EBITDA threshold for contract termination	80.00%
Five Star \| Five Star
Concentration Risk
Payments to acquire property, plant, and equipment						49,155
Amount of improvements to communities						111,603
Five Star \| Affiliated Entity \| Five Star
Concentration Risk
Annual rent as a percentage of gross revenues, percent				4.00%
Annual rent as a percentage of gross revenues, amount						$ 538
Disposal Group, Held-for-sale, Not Discontinued Operations \| Senior Living Communities
Concentration Risk
Number of properties owned (property) \| property					10	2
Number of units in real estate property \| property					820
Disposal Group, Held-for-sale, Not Discontinued Operations \| Five Star \| Senior Living Communities
Concentration Risk
Amounts of transaction	$ 682,000
Number of properties owned (property) \| community	108			108
Number of units in real estate property \| unit	1,500
Disposal Group, Disposed of by Means Other than Sale, Not Discontinued Operations \| Five Star \| Senior Living Communities
Concentration Risk
Amounts of transaction				$ 17,363
Number of units in real estate property \| unit				7,340
Acquisition and certain other transaction related costs				$ 13,311
Number of properties transitioned \| community				107
Five Star \| Senior Living Communities
Concentration Risk
Payments to acquire property, plant, and equipment		$ 49,155
Scenario, Adjustment \| Senior Living Communities
Concentration Risk
Number of properties owned (property) \| property				10
Scenario, Adjustment \| Disposal Group, Held-for-sale, Not Discontinued Operations \| Five Star \| Senior Living Communities
Concentration Risk
Number of units in real estate property \| unit	7,500
Residents fees and services \| SHOP \| Affiliated Entity \| Five Star
Concentration Risk
Revenue reserve for inadequate documentation					$ 3,842
Penalties for inadequate documentation					$ 1,921