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Real Estate Properties - Narrative (Details) $ in Thousands |  | 1 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | ---
Feb. 23, 2021 USD ($) property | Feb. 25, 2021 USD ($) property | Jan. 31, 2020 USD ($) | May 31, 2019 USD ($) building unit | Dec. 31, 2018 ft² property building community | Jun. 30, 2018 USD ($) unit building | Dec. 31, 2020 USD ($) ft² unit property building | Dec. 31, 2019 USD ($) ft² unit property building | Dec. 31, 2018 USD ($) property building community | Sep. 30, 2019 property | Jul. 31, 2019 ft² building
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Real estate investment properties, net |  |  |  |  |  |  | $ 5,715,829 | $ 5,890,785 |  |  |
Real estate property - accumulated depreciation |  |  |  |  |  |  | $ 1,694,901 | 1,570,801 |  |  |
Number of properties owned (property) | property |  |  |  |  |  |  | 397 |  |  |  |
Impairment of assets |  |  |  |  |  |  | $ 106,972 | 115,201 | $ 66,346 |  |
Gain on sale of properties |  |  |  |  |  |  | 6,487 | 39,696 | 261,916 |  |
Lease committed but unspent tenant related obligations |  |  |  |  |  |  | 19,159 | 23,994 |  |  |
Capitalized interest |  |  |  |  |  |  | 1,833 | 1,124 | 124 |  |
Land |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Real estate investment properties, net |  |  |  |  |  |  | 789,125 | 793,123 |  |  |
Buildings and Improvements |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Real estate investment properties, net |  |  |  |  |  |  | 6,621,605 | 6,668,463 |  |  |
Building |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Real estate property - accumulated depreciation |  |  |  |  |  |  | 1,561,751 | 1,428,850 |  |  |
Building Improvements |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Real estate property - accumulated depreciation |  |  |  |  |  |  | $ 133,150 | $ 141,951 |  |  |
Medical Office |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Number of properties owned (property) | property |  |  |  |  |  |  | 7 | 20 |  |  |
Impairment of assets |  |  |  |  |  |  | $ 8,558 | $ 43,035 | $ 46,797 |  |
Number of properties acquired | property |  |  |  |  |  |  |  |  | 13 |  |
Senior Living Communities |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Number of properties owned (property) | property |  |  |  |  |  |  | 28 | 25 |  |  |
Number of units in real estate property | unit |  |  |  |  |  |  | 29,335 |  |  |  |
Impairment of assets |  |  |  |  |  |  | $ 98,414 | $ 72,166 |  |  |
Gain on sale of properties |  |  |  |  |  |  | 225 |  |  |  |
Real estate improvements by lessee purchased |  |  |  |  |  |  | 2,138 | 1,739 |  |  |
Increase in annual lease rent payable |  |  |  |  |  |  | $ 135 | $ 90 |  |  |
Senior Living Communities | California Colorado And Oregon |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Number of properties owned (property) | community |  |  |  |  | 3 |  |  |  | 3 |  |
Impairment of assets |  |  |  |  |  |  |  |  | $ 19,549 |  |
Five Star |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Increase in annual lease rent payable |  |  |  |  |  |  |  |  | 1,433 |  |
Purchase price excluding closing costs |  |  |  |  |  |  |  |  | 17,956 |  |
Amount of improvements to communities |  |  |  |  |  |  |  |  | 111,603 |  |
Payments to acquire property, plant, and equipment |  |  |  |  |  |  |  |  | 49,155 |  |
Welness Centers |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Number of properties owned (property) | property |  |  |  |  |  |  | 10 |  |  |  |
Area of real estate properties (in square feet) | ft² |  |  |  |  |  |  | 812,000 |  |  |  |
Life Science |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Number of properties owned (property) | property |  |  |  |  |  |  |  | 1 |  |  |
Medical Office / Life Science |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Number of properties owned (property) | property |  |  |  |  |  |  | 123 |  |  |  |
Area of real estate properties (in square feet) | ft² |  |  |  |  |  |  | 11,300,000 |  |  |  |
Leases committed expenditure |  |  |  |  |  |  | $ 17,901 | $ 30,135 |  |  |
Area of real estate properties leased (in square feet) | ft² |  |  |  |  |  |  | 1,000,000.0 | 1,500,000 |  |  |
Senior Living Communities, Independent Living, Assisted Living, and Skilled Nursing Facility |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Number of properties owned (property) | property |  |  |  |  |  |  | 264 |  |  |  |
Land Parcel | Arizona |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Real estate purchase price |  |  | $ 2,600 |  |  |  |  |  |  |  |
Vacated | California |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Number of properties owned (property) | building |  |  |  |  |  |  |  |  |  |  | 3
Area of real estate properties (in square feet) | ft² |  |  |  |  |  |  |  |  |  |  | 164,091
Five Star |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Real estate improvements by lessee purchased |  |  |  |  |  |  |  |  | 17,956 |  |
Increase in annual lease rent payable |  |  |  |  |  |  |  |  | $ 1,433 |  |
Disposal Group, Held-for-sale, Not Discontinued Operations | Medical Office |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Number of properties owned (property) | property |  |  |  |  | 2 |  | 1 | 15 | 2 |  |
Disposal Group, Held-for-sale, Not Discontinued Operations | Senior Living Communities |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
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 | Medical Office / Life Science |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Area of real estate properties (in square feet) | ft² |  |  |  |  |  |  | 355,656 |  |  |  |
Number of units in real estate property | property |  |  |  |  |  |  | 5 |  |  |  |
Discontinued Operations, Disposed of by sale | California |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Gain on sale of properties |  |  |  |  |  | $ 2,150 |  |  |  |  |
Disposal Group, Disposed of by Sale, Not Discontinued Operations |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Number of properties owned (property) | building |  |  |  |  | 5 |  | 27 | 46 | 5 |  |
Sale price of property sold and agreed to be sold |  |  |  |  |  |  | $ 152,893 | $ 260,783 | $ 334,865 |  |
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Medical Office |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Number of properties owned (property) | property |  |  |  |  |  |  | 4 | 13 |  |  |
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Senior Living Communities |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Number of properties owned (property) | property |  |  |  |  |  |  | 9 |  |  |  |
Number of real estate properties closed | property |  |  |  |  |  |  | 7 |  |  |  |
Disposal Group, Disposed of by Sale, Not Discontinued Operations | SNF |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Number of properties owned (property) | property |  |  |  |  |  |  | 8 |  |  |  |
Number of units in real estate property | property |  |  |  |  |  |  |  |  |  | 15 |
Disposal Group, Disposed of by Sale, Not Discontinued Operations | SNF | California |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Number of properties owned (property) | building |  |  |  | 3 |  | 1 |  |  |  |  |
Number of units in real estate property | unit |  |  |  | 278 |  | 98 |  |  |  |  |
Sale price of property sold and agreed to be sold |  |  |  | $ 21,500 |  | $ 6,500 |  |  |  |  |
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Medical Office / Life Science |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Number of properties owned (property) | property |  |  |  |  |  |  |  | 5 |  |  |
Discontinued Operations, Held-for-sale | Medical Office |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Number of properties owned (property) | property |  |  |  |  | 2 |  |  |  | 2 |  |
Area of real estate properties leased (in square feet) | ft² |  |  |  |  | 32,604 |  |  |  |  |  |
Discontinued Operations, Held-for-sale | Senior Living Communities |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Number of properties owned (property) | property |  |  |  |  |  |  |  | 12 |  |  |
Number of units in real estate property | unit |  |  |  |  |  |  |  | 1,670 |  |  |
Discontinued Operations, Held-for-sale | Medical Office / Life Science |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Number of properties owned (property) | property |  |  |  |  |  |  |  | 21 |  |  |
Area of real estate properties (in square feet) | ft² |  |  |  |  |  |  |  | 875,617 |  |  |
Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations | Medical Office |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Number of properties owned (property) | property |  |  |  |  |  |  | 10 |  |  |  |
Subsequent Event | Disposal Group, Held-for-sale, Not Discontinued Operations |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Sale price of property sold and agreed to be sold |  | $ 9,000 |  |  |  |  |  |  |  |  |
Subsequent Event | Discontinued Operations, Held-for-sale |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Number of properties owned (property) | property | 4 |  |  |  |  |  |  |  |  |  |
Sale price of property sold and agreed to be sold | $ 95,500 |  |  |  |  |  |  |  |  |  |
Subsequent Event | Discontinued Operations, Held-for-sale | Medical Office / Life Science |  |  |  |  |  |  |  |  |  |  |
Real Estate Properties |  |  |  |  |  |  |  |  |  |  |
Number of properties owned (property) | property |  | 1 |  |  |  |  |  |  |  |  |

X
- Definition This element represents the aggregate purchase price of real estate properties acquired by the entity during the period. This amount includes cash paid plus debt assumed, if any, and other settlement adjustments but excludes closing costs. + References No definition available. + Details
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- Definition Represents the increase or decrease on the annual rent the lessee is obligated to pay on an operating lease. + References No definition available. + Details
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Namespace Prefix: | dhc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Amount of committed but unspent tenant related obligations based on executed lease. + References No definition available. + Details
Name: | dhc_LeaseCommittedButUnspentTenantRelatedObligations
Namespace Prefix: | dhc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Represents the amount of expenditure committed by entity relating to leases. + References No definition available. + Details
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Namespace Prefix: | dhc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Represents the number of properties acquired or agreed to be acquired by the entity. + References No definition available. + Details
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Namespace Prefix: | dhc_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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- Definition Number of Real Estate Properties Closed + References No definition available. + Details
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Namespace Prefix: | dhc_
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Balance Type: | na
Period Type: | duration

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- Definition Represents the aggregate purchase price excluding acquisition costs of real estate properties acquired or agreed to be acquired by the entity. + References No definition available. + Details
Name: | dhc_RealEstateAggregatePurchasePrice
Namespace Prefix: | dhc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition This element represents the aggregate sales price excluding closing costs, of real estate properties sold by the entity. + References No definition available. + Details
Name: | dhc_RealEstateAggregateSalesPrice
Namespace Prefix: | dhc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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- Definition Represents the amount of improvements to real estate properties made by lessees and purchased by the entity. + References No definition available. + Details
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Namespace Prefix: | dhc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Related Party Transaction, Amount Of Improvements To Communities To Leased Asset + References No definition available. + Details
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Namespace Prefix: | dhc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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- Definition Represents the area of the real estate property subject to an operating lease. + References No definition available. + Details
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Namespace Prefix: | dhc_
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Balance Type: | na
Period Type: | duration

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- 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

X
- 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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=109226348&loc=d3e2420-110228 + Details
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Period Type: | duration

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- Definition 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. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=109226691&loc=d3e2941-110230 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=109226348&loc=d3e2443-110228 + Details
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- Definition Amount of cash paid for interest capitalized, classified as investing activity. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3213-108585 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=121583591&loc=d3e4297-108586 + Details
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- Definition The number of real estate properties owned as of the balance sheet date. + References No definition available. + Details
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- Definition The number of units in a real estate property owned as of the balance sheet date. + References No definition available. + Details
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- 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=121586364&loc=d3e3213-108585 + Details
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Balance Type: | credit
Period Type: | duration

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- 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
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- Definition The cumulative amount of depreciation for real estate property held for investment purposes. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.1(3)) -URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910 + Details
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- Definition 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. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.1(d)) -URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910 + Details
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- Details
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