Summary of Significant Accounting Policies (Policies)	12 Months Ended
Dec. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation. These consolidated financial statements include the accounts of us and our subsidiaries, all of which are wholly owned directly or indirectly by us. All intercompany transactions and balances with or among our consolidated subsidiaries have been eliminated.
Real Estate Properties	Real Estate Properties. We record our properties at cost and provide depreciation on real estate investments on a straight line basis over estimated useful lives generally ranging from 7 to 40 years. 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 useful lives; however, we are ultimately responsible for the purchase price allocations and determinations of useful lives. We allocate the purchase prices of our properties to land, buildings and improvements based on determinations of the relative 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. We allocate a portion of the purchase price of our properties 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. 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. 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 the accompanying consolidated financial statements. 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. If the value of tenant relationships becomes material in the future, we may separately allocate those amounts and amortize the allocated amounts over the estimated life of the relationships. For transactions that qualify as business combinations, we allocate the excess, if any, of the consideration over the fair value of the assets acquired to goodwill. We amortize capitalized above market lease values (included in acquired real estate leases, net in our consolidated balance sheets) and below market lease values (presented as assumed real estate lease obligations, net in our consolidated balance sheets) as a reduction or increase, respectively, to rental income over the terms of the associated leases. Such amortization resulted in net decreases to rental income of $2,288, $5,440 and $2,710 during the years ended December 31, 2021, 2020 and 2019, respectively. We amortize the value of acquired in place leases (included in acquired real estate leases, net in our consolidated balance sheets), exclusive of the value of above market and below market acquired in place leases, over the terms of the associated leases. Such amortization, which is included in depreciation and amortization expense, amounted to $142,538, $161,752 and $195,268 during the years ended December 31, 2021, 2020 and 2019, respectively. If a lease is terminated prior to its stated expiration, we write off the unamortized amounts relating to that lease. We regularly evaluate whether events or changes in circumstances have occurred that could indicate an impairment in the value of long lived assets. If there is an indication that the carrying value of an asset is not recoverable, we estimate the projected undiscounted cash flows to determine if an impairment loss should be recognized. The future net undiscounted cash flows are subjective and are based in part on assumptions regarding hold periods, market rents and terminal capitalization rates. We determine the amount of any impairment loss by comparing the historical carrying value to estimated fair value. We estimate fair value through an evaluation of recent financial performance and projected discounted cash flows using standard industry valuation techniques. In addition to consideration of impairment upon the events or changes in circumstances described above, we regularly evaluate the remaining lives of our long lived assets. If we change our estimate of the remaining lives, we allocate the carrying value of the affected assets over their revised remaining lives.
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 escrowed for future real estate taxes, insurance, leasing costs, capital expenditures and debt service, as required by certain of our mortgage debts.
Deferred Leasing Costs	Deferred Leasing Costs. Deferred leasing costs include brokerage costs and inducements associated with our entering leases. We amortize deferred leasing costs, which are included in depreciation and amortization expense, and inducements, which are included as a reduction to rental income, on a straight line basis over the terms of the respective leases. Legal costs associated with the execution of our leases are expensed as incurred and included in general and administrative expenses in our consolidated statements of comprehensive income (loss). We recorded amortization of deferred leasing costs of $6,691, $5,985 and $5,216, and reductions to rental income related to the amortization of inducements of $1,187, $902 and $757 for the years ended December 31, 2021, 2020 and 2019, respectively.
Debt Issuance Costs	Debt Issuance Costs. Costs related to the issuance or assumption of debt are capitalized and amortized to interest expense over the terms of the respective loans. Debt issuance costs, net of accumulated amortization, for our revolving credit facility are included in other assets in our consolidated balance sheets. As of December 31, 2021 and 2020, debt issuance costs for our revolving credit facility were $4,125 and accumulated amortization of debt issuance costs for our revolving credit facility were $3,079 and $2,069, respectively. Debt issuance costs, net of accumulated amortization, for our senior unsecured notes and mortgage notes payable are presented as a direct deduction from the associated debt liability in our consolidated balance sheets.
Equity Securities	Equity Securities. We previously owned 2,801,060 common shares of class A common stock of The RMR Group Inc., or RMR Inc. Prior to the sale of our shares of RMR Inc. class A common stock on July 1, 2019, our equity securities were recorded at fair value based on their quoted market price at the end of each reporting period.
Equity Method Investments	Equity Method Investments. We previously accounted for our investment in Affiliates Insurance Company, or AIC, until AIC was dissolved on February 13, 2020, using the equity method of accounting. Significant influence was present through common representation on the boards of trustees or directors of us and AIC. See Note 6 for more information regarding our investment in AIC. We also have noncontrolling ownership interests of 51% and 50% in two unconsolidated joint ventures that own three properties. The properties owned by these joint ventures are encumbered by an aggregate of $82,000 of mortgage indebtedness. We do not control the activities that are most significant to these joint ventures and, as a result, we account for our investments in these joint ventures under the equity method of accounting. See Note 3 for more information regarding our unconsolidated joint ventures. We periodically evaluate our equity method investments for possible indicators of other than temporary impairment whenever events or changes in circumstances indicate the carrying amount of the investment might not be recoverable. These indicators may include the length of time and the extent to which the market value of our investment is below our carrying value, the financial condition of our investees, our intent and ability to be a long term holder of the investment and other considerations. If the decline in fair value is judged to be other than temporary, we record an impairment charge to adjust the basis of the investment to its estimated fair value.
Revenue Recognition	Revenue Recognition. We are a lessor of commercial office properties. Our leases provide our tenants with the contractual right to use and economically benefit from all of the physical space specified in the leases; therefore, we have determined to evaluate our leases as lease arrangements. Our leases provide for base rent payments and in addition may include variable payments. Rental income from operating leases, including any payments derived by index or market-based indices, is recognized on a straight line basis over the lease term when we have determined that the collectability of substantially all of the lease payments is probable. Some of our leases have options to extend or terminate the lease exercisable at the option of our tenants, which are considered when determining the lease term. Allowances for bad debts are recognized as a direct reduction of rental income. Certain of our leases contain non-lease components, such as property level operating expenses and capital expenditures reimbursed by our tenants as well as other required lease payments. We have made the policy election to not separate the lease and non-lease components because (i) the lease components are operating leases and (ii) the timing and pattern of recognition of the non-lease components are the same as those of the lease components. We apply Accounting Standards Codification 842, Leases, to the combined component. Income derived by our leases is recorded in rental income in our consolidated statements of comprehensive income (loss). Certain tenants are obligated to pay directly their obligations under their leases for insurance, real estate taxes and certain other expenses. These obligations, which have been assumed by the tenants under the terms of their respective leases, are not reflected in our consolidated financial statements. To the extent any tenant responsible for any such obligations under the applicable lease defaults on such lease or if it is deemed probable that the tenant will fail to pay for such obligations, we would record a liability for such obligations. See Note 4 for more information regarding our leases.
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, accordingly, we generally will not be subject to federal income taxes provided we distribute our taxable income and meet certain other requirements to qualify for taxation as a REIT. We are, however, subject to certain state and local taxes.
Cumulative Other Comprehensive Income	Cumulative Other Comprehensive Income (Loss). Cumulative other comprehensive income (loss) represents our share of the cumulative comprehensive income and losses of our equity method investees.
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 ownership, $.01 par value, or our common shares, outstanding during the period. We calculate diluted earnings per share using the more dilutive of the two class method or the treasury stock method. Unvested share awards and other potentially dilutive common shares, together with the related impact on earnings, are considered when calculating diluted earnings per share.
Use of Estimates	Use of Estimates. Preparation of these financial statements in conformity with 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. We operate in one business segment: direct ownership of real estate properties.
New Accounting Pronouncements	New Accounting Pronouncements. In October 2021, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or ASU, No. 2021-08, Business Combinations (Topic 805): Accounting for Contract Assets and Contract Liabilities from Contracts with Customers, or ASU No. 2021-08, which requires that an acquirer account for the related revenue contracts in accordance with Topic 606 as if it had originated the contracts. The acquiring entity shall recognize and measure the acquired contract assets and contract liabilities consistent with how they were recognized and measured in the acquiree’s financial statements, rather than at fair value at the acquisition date. ASU No. 2021-08 is effective for fiscal years beginning after December 15, 2022, with early adoption permitted. On October 1, 2021, we early adopted ASU No. 2021-08. The adoption of ASU No. 2021-08 did not have an impact on our consolidated financial statements.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2021

Basis of Presentation. These consolidated financial statements include the accounts of us and our subsidiaries, all of which are wholly owned directly or indirectly by us. All intercompany transactions and balances with or among our consolidated subsidiaries have been eliminated.

Real Estate Properties

Real Estate Properties. We record our properties at cost and provide depreciation on real estate investments on a straight line basis over estimated useful lives generally ranging from 7 to 40 years. 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 useful lives; however, we are ultimately responsible for the purchase price allocations and determinations of useful lives.

We allocate the purchase prices of our properties to land, buildings and improvements based on determinations of the relative 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. We allocate a portion of the purchase price of our properties 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. 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. 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 the accompanying consolidated financial statements. 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. If the value of tenant relationships becomes material in the future, we may separately allocate those amounts and amortize the allocated amounts over the estimated life of the relationships. For transactions that qualify as business combinations, we allocate the excess, if any, of the consideration over the fair value of the assets acquired to goodwill.

We amortize capitalized above market lease values (included in acquired real estate leases, net in our consolidated balance sheets) and below market lease values (presented as assumed real estate lease obligations, net in our consolidated balance sheets) as a reduction or increase, respectively, to rental income over the terms of the associated leases. Such amortization resulted in net decreases to rental income of $2,288, $5,440 and $2,710 during the years ended December 31, 2021, 2020 and 2019, respectively. We amortize the value of acquired in place leases (included in acquired real estate leases, net in our consolidated balance sheets), exclusive of the value of above market and below market acquired in place leases, over the terms of the associated leases. Such amortization, which is included in depreciation and amortization expense, amounted to $142,538, $161,752 and $195,268 during the years ended December 31, 2021, 2020 and 2019, respectively. If a lease is terminated prior to its stated expiration, we write off the unamortized amounts relating to that lease.

We regularly evaluate whether events or changes in circumstances have occurred that could indicate an impairment in the value of long lived assets. If there is an indication that the carrying value of an asset is not recoverable, we estimate the projected undiscounted cash flows to determine if an impairment loss should be recognized. The future net undiscounted cash flows are subjective and are based in part on assumptions regarding hold periods, market rents and terminal capitalization rates. We determine the amount of any impairment loss by comparing the historical carrying value to estimated fair value. We estimate fair value through an evaluation of recent financial performance and projected discounted cash flows using standard industry valuation techniques. In addition to consideration of impairment upon the events or changes in circumstances described above, we regularly evaluate the remaining lives of our long lived assets. If we change our estimate of the remaining lives, we allocate the carrying value of the affected assets over their revised remaining lives.

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 escrowed for future real estate taxes, insurance, leasing costs, capital expenditures and debt service, as required by certain of our mortgage debts.

Deferred Leasing Costs

Deferred Leasing Costs. Deferred leasing costs include brokerage costs and inducements associated with our entering leases. We amortize deferred leasing costs, which are included in depreciation and amortization expense, and inducements, which are included as a reduction to rental income, on a straight line basis over the terms of the respective leases. Legal costs associated with the execution of our leases are expensed as incurred and included in general and administrative expenses in our consolidated statements of comprehensive income (loss). We recorded amortization of deferred leasing costs of $6,691, $5,985 and $5,216, and reductions to rental income related to the amortization of inducements of $1,187, $902 and $757 for the years ended December 31, 2021, 2020 and 2019, respectively.

Debt Issuance Costs

Debt Issuance Costs. Costs related to the issuance or assumption of debt are capitalized and amortized to interest expense over the terms of the respective loans. Debt issuance costs, net of accumulated amortization, for our revolving credit facility are included in other assets in our consolidated balance sheets. As of December 31, 2021 and 2020, debt issuance costs for our revolving credit facility were $4,125 and accumulated amortization of debt issuance costs for our revolving credit facility were $3,079 and $2,069, respectively. Debt issuance costs, net of accumulated amortization, for our senior unsecured notes and mortgage notes payable are presented as a direct deduction from the associated debt liability in our consolidated balance sheets.

Equity Securities

Equity Securities. We previously owned 2,801,060 common shares of class A common stock of The RMR Group Inc., or RMR Inc. Prior to the sale of our shares of RMR Inc. class A common stock on July 1, 2019, our equity securities were recorded at fair value based on their quoted market price at the end of each reporting period.

Equity Method Investments

Equity Method Investments. We previously accounted for our investment in Affiliates Insurance Company, or AIC, until AIC was dissolved on February 13, 2020, using the equity method of accounting. Significant influence was present through common representation on the boards of trustees or directors of us and AIC. See Note 6 for more information regarding our investment in AIC.

We also have noncontrolling ownership interests of 51% and 50% in two unconsolidated joint ventures that own three properties. The properties owned by these joint ventures are encumbered by an aggregate of $82,000 of mortgage indebtedness. We do not control the activities that are most significant to these joint ventures and, as a result, we account for our investments in these joint ventures under the equity method of accounting. See Note 3 for more information regarding our unconsolidated joint ventures.

We periodically evaluate our equity method investments for possible indicators of other than temporary impairment whenever events or changes in circumstances indicate the carrying amount of the investment might not be recoverable. These indicators may include the length of time and the extent to which the market value of our investment is below our carrying value, the financial condition of our investees, our intent and ability to be a long term holder of the investment and other considerations. If the decline in fair value is judged to be other than temporary, we record an impairment charge to adjust the basis of the investment to its estimated fair value.

Revenue Recognition

Revenue Recognition. We are a lessor of commercial office properties. Our leases provide our tenants with the contractual right to use and economically benefit from all of the physical space specified in the leases; therefore, we have determined to evaluate our leases as lease arrangements.

Our leases provide for base rent payments and in addition may include variable payments. Rental income from operating leases, including any payments derived by index or market-based indices, is recognized on a straight line basis over the lease term when we have determined that the collectability of substantially all of the lease payments is probable. Some of our leases have options to extend or terminate the lease exercisable at the option of our tenants, which are considered when determining the lease term. Allowances for bad debts are recognized as a direct reduction of rental income.

Certain of our leases contain non-lease components, such as property level operating expenses and capital expenditures reimbursed by our tenants as well as other required lease payments. We have made the policy election to not separate the lease and non-lease components because (i) the lease components are operating leases and (ii) the timing and pattern of recognition of the non-lease components are the same as those of the lease components. We apply Accounting Standards Codification 842, Leases, to the combined component. Income derived by our leases is recorded in rental income in our consolidated statements of comprehensive income (loss).

Certain tenants are obligated to pay directly their obligations under their leases for insurance, real estate taxes and certain other expenses. These obligations, which have been assumed by the tenants under the terms of their respective leases, are not reflected in our consolidated financial statements. To the extent any tenant responsible for any such obligations under the applicable lease defaults on such lease or if it is deemed probable that the tenant will fail to pay for such obligations, we would record a liability for such obligations. See Note 4 for more information regarding our leases.

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, accordingly, we generally will not be subject to federal income taxes provided we distribute our taxable income and meet certain other requirements to qualify for taxation as a REIT. We are, however, subject to certain state and local taxes.

Cumulative Other Comprehensive Income

Cumulative Other Comprehensive Income (Loss). Cumulative other comprehensive income (loss) represents our share of the cumulative comprehensive income and losses of our equity method investees.

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 ownership, $.01 par value, or our common shares, outstanding during the period. We calculate diluted earnings per share using the more dilutive of the two class method or the treasury stock method. Unvested share awards and other potentially dilutive common shares, together with the related impact on earnings, are considered when calculating diluted earnings per share.

Use of Estimates

Use of Estimates. Preparation of these financial statements in conformity with 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. We operate in one business segment: direct ownership of real estate properties.

New Accounting Pronouncements

New Accounting Pronouncements. In October 2021, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or ASU, No. 2021-08, Business Combinations (Topic 805): Accounting for Contract Assets and Contract Liabilities from Contracts with Customers, or ASU No. 2021-08, which requires that an acquirer account for the related revenue contracts in accordance with Topic 606 as if it had originated the contracts. The acquiring entity shall recognize and measure the acquired contract assets and contract liabilities consistent with how they were recognized and measured in the acquiree’s financial statements, rather than at fair value at the acquisition date. ASU No. 2021-08 is effective for fiscal years beginning after December 15, 2022, with early adoption permitted. On October 1, 2021, we early adopted ASU No. 2021-08. The adoption of ASU No. 2021-08 did not have an impact on our consolidated financial statements.