Summary of Significant Accounting Policies (Policies)	12 Months Ended
Dec. 31, 2022
Accounting Policies [Abstract]
BASIS OF PRESENTATION	BASIS OF PRESENTATION. Our consolidated financial statements include the accounts of Diversified Healthcare Trust, we, us or our, and our subsidiaries, all of which are 100% owned directly or indirectly by us as of December 31, 2022. All intercompany transactions and balances with or among our consolidated subsidiaries have been eliminated.
REAL ESTATE PROPERTIES	REAL ESTATE PROPERTIES. We record properties at our cost and calculate depreciation on real estate investments on a straight line basis over estimated useful lives generally up to 40 years. We allocate the purchase prices of our properties to land, building and improvements based on determinations of the fair values of these assets assuming the properties are vacant. We determine the fair value of each property using methods similar to those used by independent appraisers, which may involve estimated cash flows that are based on a number of factors, including capitalization rates and discount rates, among others. In some circumstances, we engage independent real estate appraisal firms to provide market information and evaluations which are relevant to our purchase price allocations and determinations of depreciable useful lives; however, we are ultimately responsible for the purchase price allocations and determinations of useful lives. We allocate a portion of the purchase price to above market and below market leases based on the present value (using an interest rate which reflects the risks associated with acquired in place leases at the time each property was acquired by us) of the difference, if any, between (i) the contractual amounts to be paid pursuant to the acquired in place leases and (ii) our estimates of fair market lease rates for the corresponding leases, measured over a period equal to the terms of the respective leases. The terms of below market leases that include bargain renewal options, if any, are further adjusted if we determine that renewal is probable. We allocate a portion of the purchase price to acquired in place leases and tenant relationships based upon market estimates to lease up the property based on the leases in place at the time of purchase. In making these allocations, we consider factors such as estimated carrying costs during the expected lease up periods, including real estate taxes, insurance and other operating income and expenses and costs, such as leasing commissions, legal and other related expenses, to execute similar leases in current market conditions at the time a property was acquired by us. We allocate this aggregate value between acquired in place lease values and tenant relationships based on our evaluation of the specific characteristics of each tenant's lease. However, we have not separated the value of tenant relationships from the value of acquired in place leases because such value and related amortization expense is immaterial to our consolidated financial statements. If the value of tenant relationships becomes material in the future, we may separately allocate those amounts and amortize the allocated amount over the estimated life of the relationships. We amortize capitalized above market lease values (included in acquired real estate leases and other intangible assets, net in our consolidated balance sheets) as a reduction to rental income over the remaining non-cancelable terms of the respective leases. We amortize capitalized below market lease values (included in other liabilities in our consolidated balance sheets) as an increase to rental income over the non-cancelable periods of the respective leases. For the years ended December 31, 2022, 2021 and 2020, such amortization resulted in a net increase in rental income of $(245), $7,211 and $7,405, respectively. We amortize the value of in place leases exclusive of the value of above market and below market in place leases to expense over the remaining non-cancelable periods of the respective leases. During the years ended December 31, 2022, 2021 and 2020, such amortization included in depreciation totaled $11,524, $42,783 and $48,669, respectively. If a lease is terminated prior to its stated expiration, the unamortized amount relating to that lease is written off.
CASH AND CASH EQUIVALENTS	CASH AND CASH EQUIVALENTS. We consider highly liquid investments with original maturities of three months or less at the date of purchase to be cash equivalents.
RESTRICTED CASH	RESTRICTED CASH. Restricted cash consists of amounts held as collateral pursuant to our credit agreement and amounts escrowed for real estate taxes, insurance and capital expenditures at certain of our mortgaged properties. Prior to the deconsolidation of the Seaport JV, restricted cash also consisted of cash held for the operations of this joint venture.
INVESTMENTS IN EQUITY SECURITIES	INVESTMENTS IN EQUITY SECURITIES. We classify the common shares we own of AlerisLife Inc., or AlerisLife, as an equity method investment. This equity method investment is included in investments in equity securities in our consolidated balance sheets.
EQUITY METHOD INVESTMENTS	EQUITY METHOD INVESTMENTS. As of December 31, 2022, we owned a 10% equity interest in our unconsolidated Seaport JV and a 20% equity interest in an unconsolidated joint venture for 10 medical office and life science properties, or the LSMD JV. The property owned by the Seaport JV is encumbered by an aggregate $620,000 of mortgage debts. The properties owned by the LSMD JV are encumbered by an aggregate $456,625 of mortgage debts. We do not control the activities that are most significant to these joint ventures and, as a result, we account for our investment in these joint ventures under the equity method of accounting under the fair value option. See Notes 3, 10 and 11 for more information regarding these joint ventures.
DEBT ISSUANCE COSTS	DEBT ISSUANCE COSTS. Debt issuance costs include issuance or assumption costs related to borrowings and we amortize those costs as interest expense over the terms of the respective loans.
DEFERRED LEASING COSTS	DEFERRED LEASING COSTS. Deferred leasing costs include capitalized brokerage costs and inducements associated with the successful negotiation of leases. We amortize deferred leasing costs, which are included in depreciation and amortization expense, and inducements, which are included as a reduction in rental income, on a straight line basis over the terms of the respective leases. Deferred leasing costs are included in other assets, net in our consolidated balance sheets.
REVENUE RECOGNITION	REVENUE RECOGNITION. We are a lessor of medical office and life science properties, senior living communities and other healthcare related properties. Our leases provide our tenants with the contractual right to use and economically benefit from all of the premises demised under the leases; therefore, we have determined to evaluate our leases as lease arrangements.
PER COMMON SHARE AMOUNTS	PER COMMON SHARE AMOUNTS. We calculate basic earnings per common share by dividing net income (loss) by the weighted average number of our common shares of beneficial interest, $.01 par value, or our common shares, outstanding during the period. We calculate diluted earnings per common share using the more dilutive of the two class method or the treasury stock method. Unvested share awards and other potentially dilutive common shares and the related impact on earnings, are considered when calculating diluted earnings per share.
INCOME TAXES	INCOME TAXES. We have elected to be taxed as a REIT under the United States Internal Revenue Code of 1986, as amended, and as such are generally not subject to federal and most state income taxation on our operating income provided we distribute our taxable income to our shareholders and meet certain organization and operating requirements. We do, however, lease our managed senior living communities to our wholly owned TRSs that, unlike most of our subsidiaries, file a separate consolidated federal corporate income tax return and are subject to federal and state income taxes. Our consolidated income tax provision includes the income tax provision related to the operations of our TRSs and certain state income taxes we incur despite our taxation as a REIT. The Income Taxes Topic of the Codification prescribes how we should recognize, measure and present in our financial statements uncertain tax positions that have been taken or are expected to be taken in a tax return. Tax benefits are recognized to the extent that it is “more likely than not” that a particular tax position will be sustained upon examination or audit. To the extent the “more likely than not” standard has been satisfied, the benefit associated with a tax position is measured as the largest amount that has a greater than 50% likelihood of being realized upon settlement. We classify interest and penalties related to uncertain tax positions, if any, in our financial statements as a component of general and administrative expense.
USE OF ESTIMATES	USE OF ESTIMATES. Preparation of these financial statements in conformity with accounting principles generally accepted in the United States, or GAAP, requires us to make estimates and assumptions that may affect the amounts reported in these consolidated financial statements and related notes. The actual results could differ from these estimates. Significant estimates in the consolidated financial statements include purchase price allocations, useful lives of fixed assets and assessment of impairment of real estate and the related intangibles.
SEGMENT REPORTING	SEGMENT REPORTING. As of December 31, 2022, we operate in, and report financial information for, the following two segments: our portfolio of medical office and life science properties, or our Office Portfolio, and SHOP. We aggregate each of these two reporting segments based on their similar operating and economic characteristics.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2022

BASIS OF PRESENTATION. Our consolidated financial statements include the accounts of Diversified Healthcare Trust, we, us or our, and our subsidiaries, all of which are 100% owned directly or indirectly by us as of December 31, 2022. All intercompany transactions and balances with or among our consolidated subsidiaries have been eliminated.

REAL ESTATE PROPERTIES

REAL ESTATE PROPERTIES. We record properties at our cost and calculate depreciation on real estate investments on a straight line basis over estimated useful lives generally up to 40 years.

We allocate the purchase prices of our properties to land, building and improvements based on determinations of the fair values of these assets assuming the properties are vacant. We determine the fair value of each property using methods similar to those used by independent appraisers, which may involve estimated cash flows that are based on a number of factors, including capitalization rates and discount rates, among others. In some circumstances, we engage independent real estate appraisal firms to provide market information and evaluations which are relevant to our purchase price allocations and determinations of depreciable useful lives; however, we are ultimately responsible for the purchase price allocations and determinations of useful lives. We allocate a portion of the purchase price to above market and below market leases based on the present value (using an interest rate which reflects the risks associated with acquired in place leases at the time each property was acquired by us) of the difference, if any, between (i) the contractual amounts to be paid pursuant to the acquired in place leases and (ii) our estimates of fair market lease rates for the corresponding leases, measured over a period equal to the terms of the respective leases. The terms of below market leases that include bargain renewal options, if any, are further adjusted if we determine that renewal is probable. We allocate a portion of the purchase price to acquired in place leases and tenant relationships based upon market estimates to lease up the property based on the leases in place at the time of purchase. In making these allocations, we consider factors such as estimated carrying costs during the expected lease up periods, including real estate taxes, insurance and other operating income and expenses and costs, such as leasing commissions, legal and other related expenses, to execute similar leases in current market conditions at the time a property was acquired by us. We allocate this aggregate value between acquired in place lease values and tenant relationships based on our evaluation of the specific characteristics of each tenant's lease. However, we have not separated the value of tenant relationships from the value of acquired in place leases because such value and related amortization expense is immaterial to our consolidated financial

statements. If the value of tenant relationships becomes material in the future, we may separately allocate those amounts and amortize the allocated amount over the estimated life of the relationships.

We amortize capitalized above market lease values (included in acquired real estate leases and other intangible assets, net in our consolidated balance sheets) as a reduction to rental income over the remaining non-cancelable terms of the respective leases. We amortize capitalized below market lease values (included in other liabilities in our consolidated balance sheets) as an increase to rental income over the non-cancelable periods of the respective leases. For the years ended December 31, 2022, 2021 and 2020, such amortization resulted in a net increase in rental income of $(245), $7,211 and $7,405, respectively. We amortize the value of in place leases exclusive of the value of above market and below market in place leases to expense over the remaining non-cancelable periods of the respective leases. During the years ended December 31, 2022, 2021 and 2020, such amortization included in depreciation totaled $11,524, $42,783 and $48,669, respectively. If a lease is terminated prior to its stated expiration, the unamortized amount relating to that lease is written off.

CASH AND CASH EQUIVALENTS

CASH AND CASH EQUIVALENTS. We consider highly liquid investments with original maturities of three months or less at the date of purchase to be cash equivalents.

RESTRICTED CASH

RESTRICTED CASH. Restricted cash consists of amounts held as collateral pursuant to our credit agreement and amounts escrowed for real estate taxes, insurance and capital expenditures at certain of our mortgaged properties. Prior to the deconsolidation of the Seaport JV, restricted cash also consisted of cash held for the operations of this joint venture.

INVESTMENTS IN EQUITY SECURITIES

INVESTMENTS IN EQUITY SECURITIES. We classify the common shares we own of AlerisLife Inc., or AlerisLife, as an equity method investment. This equity method investment is included in investments in equity securities in our consolidated balance sheets.

EQUITY METHOD INVESTMENTS

EQUITY METHOD INVESTMENTS. As of December 31, 2022, we owned a 10% equity interest in our unconsolidated Seaport JV and a 20% equity interest in an unconsolidated joint venture for 10 medical office and life science properties, or the LSMD JV. The property owned by the Seaport JV is encumbered by an aggregate $620,000 of mortgage debts. The properties owned by the LSMD JV are encumbered by an aggregate $456,625 of mortgage debts. We do not control the activities that are most significant to these joint ventures and, as a result, we account for our investment in these joint ventures under the equity method of accounting under the fair value option. See Notes 3, 10 and 11 for more information regarding these joint ventures.

DEBT ISSUANCE COSTS

DEBT ISSUANCE COSTS. Debt issuance costs include issuance or assumption costs related to borrowings and we amortize those costs as interest expense over the terms of the respective loans.

DEFERRED LEASING COSTS

DEFERRED LEASING COSTS. Deferred leasing costs include capitalized brokerage costs and inducements associated with the successful negotiation of leases. We amortize deferred leasing costs, which are included in depreciation and amortization expense, and inducements, which are included as a reduction in rental income, on a straight line basis over the terms of the respective leases. Deferred leasing costs are included in other assets, net in our consolidated balance sheets.

REVENUE RECOGNITION

REVENUE RECOGNITION. We are a lessor of medical office and life science properties, senior living communities and other healthcare related properties. Our leases provide our tenants with the contractual right to use and economically benefit from all of the premises demised under the leases; therefore, we have determined to evaluate our leases as lease arrangements.

PER COMMON SHARE AMOUNTS

PER COMMON SHARE AMOUNTS. We calculate basic earnings per common share by dividing net income (loss) by the weighted average number of our common shares of beneficial interest, $.01 par value, or our common shares, outstanding during the period. We calculate diluted earnings per common share using the more dilutive of the two class method or the treasury stock method. Unvested share awards and other potentially dilutive common shares and the related impact on earnings, are considered when calculating diluted earnings per share.

INCOME TAXES

INCOME TAXES. We have elected to be taxed as a REIT under the United States Internal Revenue Code of 1986, as amended, and as such are generally not subject to federal and most state income taxation on our operating income provided we distribute our taxable income to our shareholders and meet certain organization and operating requirements. We do, however, lease our managed senior living communities to our wholly owned TRSs that, unlike most of our subsidiaries, file a separate consolidated federal corporate income tax return and are subject to federal and state income taxes. Our consolidated income tax provision includes the income tax provision related to the operations of our TRSs and certain state income taxes we incur despite our taxation as a REIT.

The Income Taxes Topic of the Codification prescribes how we should recognize, measure and present in our financial statements uncertain tax positions that have been taken or are expected to be taken in a tax return. Tax benefits are recognized to the extent that it is “more likely than not” that a particular tax position will be sustained upon examination or audit. To the extent the “more likely than not” standard has been satisfied, the benefit associated with a tax position is measured as the largest amount that has a greater than 50% likelihood of being realized upon settlement. We classify interest and penalties related to uncertain tax positions, if any, in our financial statements as a component of general and administrative expense.

USE OF ESTIMATES

USE OF ESTIMATES. Preparation of these financial statements in conformity with accounting principles generally accepted in the United States, or GAAP, requires us to make estimates and assumptions that may affect the amounts reported in these consolidated financial statements and related notes. The actual results could differ from these estimates. Significant estimates in the consolidated financial statements include purchase price allocations, useful lives of fixed assets and assessment of impairment of real estate and the related intangibles.

SEGMENT REPORTING

SEGMENT REPORTING. As of December 31, 2022, we operate in, and report financial information for, the following two segments: our portfolio of medical office and life science properties, or our Office Portfolio, and SHOP. We aggregate each of these two reporting segments based on their similar operating and economic characteristics.