Summary of Significant Accounting Policies	3 Months Ended
Mar. 31, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation – The accompanying financial statements have been prepared by management in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”) for interim financial information and in compliance with the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”). These unaudited consolidated financial statements and related notes should be read in conjunction with the audited consolidated financial statements and related notes and management’s discussion and analysis included in our Annual Report on Form 10-K for the year ended December 31, 2020, filed with the SEC on February 26, 2021. The consolidated balance sheet data included herein as of December 31, 2020 was derived from audited financial statements, but does not include all disclosures required by U.S. GAAP. In the opinion of management, all adjustments (consisting of normal recurring adjustments) considered necessary for a fair presentation have been included. As outlined in our Annual Report on Form 10-K for the year ended December 31, 2020, the Operating Partnership meets the definition and criteria of a variable interest entity (“VIE”) in accordance with Accounting Standards Codification (“ASC”) Topic 810 Consolidation, and the Company is the primary beneficiary of the VIE. The Company’s only material asset is its ownership interest in the Operating Partnership, and consequently, all of its assets and liabilities represent those assets and liabilities of the Operating Partnership. The Company’s debt is an obligation of the Operating Partnership where the creditors may have recourse, under certain circumstances, against the credit of the Company. Use of Estimates – The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Significant items subject to such estimates and assumptions include the useful lives of fixed assets, allowances for doubtful accounts and deferred tax assets and the valuation of derivatives, real estate assets, acquired intangible assets and certain accruals. The impacts of the COVID-19 pandemic increases uncertainty, which has reduced our ability to use past results to estimate future performance. Accordingly, our estimates and judgments may be subject to greater volatility than has been the case in the past. Principles of Consolidation – The consolidated financial statements of QTS Realty Trust, Inc. include the accounts of QTS Realty Trust, Inc. and its controlled subsidiaries. All significant intercompany accounts and transactions have been eliminated in the financial statements. We evaluate our investments in less than wholly owned entities to determine whether they should be recorded on a consolidated basis. The percentage of ownership interest in the entity, an evaluation of control and whether a VIE exists are all considered in our consolidation assessment. Investments in real estate entities which we have the ability to exercise significant influence, but do not have financial or operating control, are accounted for using the equity method of accounting. Accordingly, our share of the earnings or losses of these entities is included in consolidated net income (loss). Variable Interest Entities (VIEs) – We determine whether an entity is a VIE and, if so, whether it should be consolidated by utilizing judgments and estimates that are inherently subjective. The determination of whether an entity in which we hold a direct or indirect variable interest is a VIE is based on several factors, including whether the entity’s total equity investment at risk upon inception is sufficient to finance the entity’s activities without additional subordinated financial support. We make judgments regarding the sufficiency of the equity at risk based first on a qualitative analysis, and then a quantitative analysis, if necessary. We analyze any investments in VIEs to determine if we are the primary beneficiary. In evaluating whether we are the primary beneficiary, we evaluate our direct and indirect economic interests in the entity. Determining which reporting entity, if any, is the primary beneficiary of a VIE is primarily a qualitative approach focused on identifying which reporting entity has both (1) the power to direct the activities of a VIE that most significantly impact such entity’s economic performance and (2) the obligation to absorb losses or the right to receive benefits from such entity that could potentially be significant to such entity. Performance of that analysis requires the exercise of judgment. We consider a variety of factors in identifying the entity that holds the power to direct matters that most significantly impact the VIE’s economic performance including, but not limited to, the ability to direct financing, leasing, construction and other operating decisions and activities. In addition, we consider the rights of other investors to participate in those decisions, to replace the manager and to sell or liquidate the entity. We determine whether we are the primary beneficiary of a VIE at the time we become involved with a variable interest entity and reconsider that conclusion upon a reconsideration event. As of March 31, 2021, we had one unconsolidated entity that was considered a VIE for which we are not the primary beneficiary. Our maximum exposure to losses associated with this VIE is limited to our net investment, which was approximately $25.9 million as of March 31, 2021. Real Estate Assets – Real estate assets are reported at cost. All capital improvements for the income-producing properties that extend their useful lives are capitalized to individual property improvements and depreciated over their estimated useful lives. Depreciation for real estate assets is generally provided on a straight-line basis over 40 years from the date the property was placed in service. Property improvements are depreciated on a straight-line basis over the life of the respective improvement ranging from 20 to 40 years from the date the components were placed in service. Leasehold improvements are depreciated over the lesser of 20 years or through the end of the respective life of the lease. Repairs and maintenance costs are expensed as incurred. For the three months ended March 31, 2021, depreciation expense related to real estate assets and non-real estate assets was $42.7 million and $2.9 million, respectively, for a total of $45.6 million. For the three months ended March 31, 2020, depreciation expense related to real estate assets and non-real estate assets was $32.3 million and $3.4 million, respectively, for a total of $35.7 million. We capitalize certain real estate development costs, including internal costs incurred in connection with development. The capitalization of costs during the construction period (including interest and related loan fees, property taxes and other direct and indirect project costs) begins when development efforts commence and ends when the asset is ready for its intended use. The capitalization of internal costs increases construction in progress recognized during development of the related property and the cost of the real estate asset when placed into service and such costs are depreciated over its estimated useful life. Capitalization of such costs, excluding interest, aggregated to $5.5 million and $4.5 million for the three months ended March 31, 2021 and 2020, respectively. Interest is capitalized during the period of development by applying our weighted average effective borrowing rate to the actual development and other capitalized costs paid during the construction period. Interest is capitalized until the property is ready for its intended use. Interest costs capitalized totaled $7.0 million and $8.1 million for the three months ended March 31, 2021 and 2020, respectively. Acquisitions and Sales – Acquisitions of real estate and other entities are either accounted for as asset acquisitions or business combinations depending on facts and circumstances. In developing estimates of fair value of acquired assets and assumed liabilities, management analyzes a variety of factors including market data, estimated future cash flows of the acquired operations, industry growth rates, current replacement cost for fixed assets and market rate assumptions for contractual obligations. Such a valuation requires management to make significant estimates and assumptions, particularly with respect to the intangible assets. Impairment of Long-Lived Assets, Intangible Assets and Goodwill – We review our long-lived assets, intangible assets and equity method investments for impairment when events or changes in circumstances indicate that the carrying amount of the assets may not be recoverable. Recoverability of assets to be held and used is measured by comparison of the carrying amount to the future net cash flows, undiscounted and without interest, expected to be generated by the asset group. If the net carrying value of the asset group exceeds the value of the undiscounted cash flows, the fair value of the asset group is assessed and may be considered impaired. An impairment loss is recognized based on the excess of the carrying amount of the impaired asset over its fair value. No impairment losses were recorded for the three months ended March 31, 2021 and March 31, 2020. The fair value of goodwill is the consideration transferred in a business combination which is not allocable to identifiable intangible and tangible assets. Goodwill is subject to at least an annual assessment for impairment. In connection with the goodwill impairment evaluation that we performed as of October 1, 2020, we determined qualitatively that it is not more likely than not that the fair value of our one reporting unit was less than the carrying amount, thus we did not perform a quantitative analysis. As we continue to operate and assess our goodwill at the consolidated level for our single reporting unit and our market capitalization significantly exceeds our net asset value, further analysis was not deemed necessary as of March 31, 2021. Cash and Cash Equivalents – We consider all demand deposits and money market accounts purchased with a maturity date of three months or less at the date of purchase to be cash equivalents. Our account balances at one or more institutions periodically exceed the Federal Deposit Insurance Corporation (“FDIC”) insurance coverage and, as a result, there is concentration of credit risk related to amounts on deposit in excess of FDIC coverage. We mitigate this risk by depositing a majority of our funds with several major financial institutions. We also have not experienced any losses and do not believe that the risk is significant. Revenue Recognition – We derive our revenues from leases with customers for data center space which include lease components and nonlease revenue components, such as power, tenant recoveries, and managed services. We have elected the available practical expedient under ASC Topic 842, Leases, to combine our nonlease revenue components that have the same pattern of transfer as the related operating lease component into a single combined lease component. The single combined component is accounted for under ASC Topic 842 if the lease component is the predominant component and is accounted for under ASC Topic 606 if the nonlease components are the predominant components. In our contracts, the single combined component is accounted for under ASC Topic 842 as the lease component is the predominant component. A description of each of our disaggregated revenue streams is as follows: Rental Revenue Our leases with customers are classified as operating leases and rental revenue is recognized on a straight-line basis over the customer lease term. Occasionally, customer leases include options to extend or terminate the lease agreements. We do not include any of these extension or termination options in a customer’s lease term for lease classification purposes or recognizing rental revenue unless it is reasonably certain the customer will exercise these extension or termination options. Rental revenue also includes revenue from power delivery on fixed power arrangements, whereby customers are billed and pay a fixed monthly fee per committed available amount of connected power. These fixed power arrangements require us to provide a series of distinct services and to stand ready to deliver the power over the contracted term which is co-terminus with the lease. Customer fixed power arrangements have the same pattern of transfer over the lease term as the lease component and are therefore combined with the lease component to form a single lease component that is recognized over the term of the lease on a straight-line basis. In addition, rental revenue includes straight-line rent. Straight-line rent represents the difference in rents recognized during the period versus amounts contractually due pursuant to the underlying leases and is recorded as deferred rent receivable/payable in the consolidated balance sheets. For lease agreements that provide for scheduled rent increases, rental income is recognized on a straight-line basis over the non-cancellable term of the leases, which commences when control of the space has been provided to the customer. The amount of the straight-line rent receivable on the balance sheet included in rents and other receivables, net was $71.0 million and $63.6 million as of March 31, 2021 and December 31, 2020, respectively. Rental revenue also includes amortization of set-up fees which are amortized over the term of the respective lease as discussed below in the "Deferred Income" section. Variable Lease Revenue from Recoveries Certain customer leases contain provisions under which customers reimburse us for power and cooling-related charges as well as a portion of the property’s real estate taxes, insurance and other operating expenses. Recoveries of power and cooling-related expenses relate specifically to our variable power arrangements, whereby customers pay variable monthly fees for the specific amount of power utilized at the current utility rates. Our performance obligation is to stand ready to deliver power over the life of the customer contract up to a contracted power capacity. Customers have the flexibility to increase or decrease the amount of power consumed, and therefore sub-metered power revenue is constrained at contract inception. The reimbursements are included in revenue as recoveries from customers and are recognized each month as the uncertainty related to the consideration is resolved (i.e. we provide power to our customers) and customers utilize the power. Reimbursement of real estate taxes, insurance, common area maintenance, or other operating expenses are accounted for as variable payments under lease guidance pursuant to the practical expedient and are recognized as revenue in the period that the expenses are recognized. Variable lease revenue from recoveries discussed above, including power, common area maintenance or other operating costs, have the same pattern of transfer over the lease term as the lease component and are therefore combined with the lease component to form a single lease component. Variable lease revenue from recoveries is included within the “rental” line item on the statements of operations. Other Revenue Other revenue primarily consists of revenue from our managed service offerings, as well as revenue earned from partner channel, management and development fees. We, through our taxable REIT subsidiaries (“TRS”), may provide use of our managed services to our customers on an individual or combined basis. In our managed services offering, the TRS’s performance obligation is to provide services (e.g. cloud hosting, data backup, data storage or data center personnel labor hours) to facilitate a fully integrated information technology (“IT”) outsourcing environment over a contracted term. Although underlying services may vary, over the contracted term monthly service offerings are substantially the same and we account for the services as a series of distinct services in accordance with ASC Topic 606. Service fee revenue is recognized as the revenue is earned, which generally coincides with the services being provided. As we have the right to consideration from customers in an amount that corresponds directly with the value to the customer of the TRS’s performance of providing continuous services, we recognize monthly revenue for the amount invoiced. With respect to the transaction price allocated to remaining performance obligations within our managed service contracts, we have elected to use the optional exemption provided by ASC Topic 606 whereby we are not required to estimate the total transaction price allocated to remaining performance obligations as we apply the “right-to-invoice” practical expedient. As described above, the nature of our performance obligation in these contracts is to provide monthly services that are substantially the same and accounted for as a series of distinct services. These contracts generally have a remaining term ranging from month-to-month to three years. Management fees and other revenues are generally received from our unconsolidated entity properties as well as third parties. Management fee revenue is earned based on a contractual percentage of unconsolidated entity property revenue. Development fee revenue is earned on a contractual percentage of hard costs to develop a property. We recognize revenue for these services provided when earned based on the performance criteria in ASC Topic 606, with such revenue recorded in “Other” revenue on the consolidated statements of operations. Leases as Lessee – We determine if an arrangement is a lease at inception. If the contract is considered a lease, we evaluate leased property to determine whether the lease should be classified as a finance or operating lease in accordance with U.S. GAAP. We periodically enter into finance leases for certain data center facilities, equipment, and fiber optic transmission cabling. Finance lease assets are included within the “Buildings, improvements and equipment” line item of the consolidated balance sheets and finance lease liabilities are included within “Finance leases” line item of the consolidated balance sheets. In addition, we lease certain real estate (primarily land or real estate space) under operating lease agreements with such assets included within the “Operating lease right of use assets, net” line item of the consolidated balance sheets and the associated lease liabilities included within the “Operating lease liabilities” line item on the consolidated balance sheets. Right of use (“ROU”) assets represent our right to use an underlying asset for the lease term and lease liabilities represent our obligation to make lease payments arising from the lease. ROU assets and lease liabilities are recognized at the commencement date based on the present value of lease payments over the lease term. Certain of our leases include variable payments, which may vary based upon changes in facts or circumstances after the start of the lease. Variable lease payments are excluded from the ROU assets and lease liabilities and are recognized in the period in which the obligation for those payments is incurred. As our leases as lessee typically do not provide an implicit rate, we use our incremental borrowing rate based on the information available at the commencement date in determining the present value of lease payments. We assess multiple variables when determining the incremental borrowing rate, such as lease term, payment terms, collateral, economic conditions, and creditworthiness. ROU assets also include any lease payments made and exclude lease incentives. Many of our lease agreements include options to extend the lease, which we do not include in our expected lease terms unless they are reasonably certain to be exercised. Rental expense for lease payments related to operating leases is recognized on a straight-line basis over the lease term. Allowance for Uncollectible Accounts Receivable – We record a provision for uncollectible accounts if a receivable balance relating to lease components from an individual contract is considered by management not to be probable of collection, and this provision is recorded as a reduction to leasing revenues. We also record a general provision of estimated uncollectible tenant receivables based on general probability of collection in accordance with ASC 450-20 Loss Contingencies. This provision is recorded as bad debt expense and recorded within the “Property Operating Costs” line item of the consolidated statements of operations. The aggregate allowance for doubtful accounts on the consolidated balance sheets was $5.3 million and $5.4 million as of March 31, 2021 and December 31, 2020, respectively. Deferred Income – Deferred income generally results from non-refundable charges paid by the customer at lease inception to prepare their space for occupancy. We record this initial payment, commonly referred to as set-up fees, as a deferred income liability which amortizes into rental revenue over the term of the related lease on a straight-line basis. Deferred income was $93.5 million and $85.4 million as of March 31, 2021 and December 31, 2020, respectively. Additionally, $6.4 million and $3.9 million of deferred income was amortized into revenue for the three months ended March 31, 2021 and 2020, respectively. Equity-based Compensation – Equity-based compensation costs are measured based upon their estimated fair value on the date of grant or modification and amortized ratably over their respective service periods. We have elected to account for forfeitures as they occur. Equity-based compensation expense was $6.9 million and $4.9 million for the three months ended March 31, 2021 and 2020, respectively. Segment Information – We manage our business as one operating segment and thus one reportable segment consisting of a portfolio of investments in multiple data centers. Customer Concentrations – During the three months ended March 31, 2021, one of our customers exceeded 10% of total revenues, representing approximately 11% of total revenues for the three months ended March 31, 2021. As of March 31, 2021, three of our customers exceeded 5% of trade accounts receivable (which excludes straight-line rent receivables). In aggregate, these three customers accounted for approximately 53% of trade accounts receivable. One of these customers individually exceeded 10% of total trade accounts receivable representing 40% of total trade accounts receivable. Income Taxes – We provide for income taxes during interim periods based on the estimated effective tax rate for the year and any discrete adjustments. The effective tax rate is subject to change in the future due to various factors such as the operating performance of the taxable REIT subsidiaries, tax law changes, and future business acquisitions or divestitures. The taxable subsidiaries’ effective tax rates were (7.8)% and 13.0% for the three months ended March 31, 2021 and 2020, respectively. Fair Value Measurements – ASC Topic 820, Fair Value Measurement, emphasizes that fair value is a market-based measurement, not an entity-specific measurement. Therefore, a fair value measurement should be determined based on the assumptions that market participants would use in pricing the asset or liability. As a basis for considering market participant assumptions in fair value measurements, a fair value hierarchy is established that distinguishes between market participant assumptions based on market data obtained from sources independent of the reporting entity (observable inputs that are classified within Levels 1 and 2 of the hierarchy) and the reporting entity’s own assumptions about market participant assumptions (unobservable inputs classified within Level 3 of the hierarchy). Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets or liabilities that we have the ability to access. Level 2 inputs are inputs other than quoted prices included in Level 1 that are observable for the asset or liability, either directly or indirectly. Level 2 inputs may include quoted prices for similar assets and liabilities in active markets, as well as inputs that are observable for the asset or liability (other than quoted prices), such as interest rates, foreign exchange rates, and yield curves that are observable at commonly quoted intervals. Level 3 inputs are unobservable inputs for the asset or liability, which are typically based on an entity’s own assumptions, as there is little, if any, related market activity. In instances where the determination of the fair value measurement is based on inputs from different levels of the fair value hierarchy, the level in the fair value hierarchy within which the entire fair value measurement falls is based on the lowest level input that is significant to the fair value measurement in its entirety. Our assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment, and considers factors specific to the asset or liability. As of March 31, 2021, we valued our derivative instruments primarily utilizing Level 2 inputs. See Note 14 – ‘Fair Value of Financial Instruments’ for additional details. New Accounting Pronouncements In January 2020, the FASB issued ASU 2020-1, Investments—Equity Securities (Topic 321), Investments—Equity Method and Joint Ventures (Topic 323), and Derivatives and Hedging (Topic 815): Clarifying the Interactions between Topic 321, Topic 323, and Topic 815, which clarifies the interaction between the accounting for equity securities under Topic 321, the accounting for equity method investments in Topic 323, and the accounting for certain forward contracts and purchased options in Topic 815. ASU 2020-1 is effective for fiscal years beginning after December 15, 2020, and interim periods within those fiscal years. We adopted this ASU effective January 1, 2021, and the provisions of the standard did not have a material impact on our consolidated financial statements. In March 2020, the FASB issued ASU 2020-4, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting. ASU 2020-4 contains practical expedients for reference rate reform related activities that impact debt, leases, derivatives and other contracts. The guidance in ASU 2020-4 is optional and may be elected over time as reference rate reform activities occur. The standard is effective for all entities as of March 12, 2020 through December 31, 2022. An entity can elect to apply the amendments as of any date from the beginning of an interim period that includes or is subsequent to March 12, 2020, or prospectively from a date within an interim period that includes or is subsequent to March 12, 2020, up to that date that the financial statements are available to be issued. In January 2021, the FASB issued ASU 2021-1 Reference Rate Reform (Topic 848): Scope, which updated the standard to clarify that certain optional expedients and exceptions in Topic 848 for contract modifications and hedge accounting apply to derivatives that are affected by the discounting transition. Beginning in the first quarter of 2020, we have applied the hedge accounting expedients related to probability and the assessments of effectiveness for future LIBOR-indexed cash flows to assume that the index upon which future hedged transactions will be based matches the index on the corresponding derivatives. Application of these expedients preserves the presentation of derivatives consistent with past presentation. We continue to evaluate the impact of the guidance but we do not expect the provisions of the standard will have a material impact on our consolidated financial statements. We determined all other recently issued accounting pronouncements will not have a material impact on our consolidated financial statements or do not materially apply to our operations.

Basis of Presentation – The accompanying financial statements have been prepared by management in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”) for interim financial information and in compliance with the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”). These unaudited consolidated financial statements and related notes should be read in conjunction with the audited consolidated financial statements and related notes and management’s discussion and analysis included in our Annual Report on Form 10-K for the year ended December 31, 2020, filed with the SEC on February 26, 2021. The consolidated balance sheet data included herein as of December 31, 2020 was derived from audited financial statements, but does not include all disclosures required by U.S. GAAP. In the opinion of management, all adjustments (consisting of normal recurring adjustments) considered necessary for a fair presentation have been included.

As outlined in our Annual Report on Form 10-K for the year ended December 31, 2020, the Operating Partnership meets the definition and criteria of a variable interest entity (“VIE”) in accordance with Accounting Standards Codification (“ASC”) Topic 810 Consolidation, and the Company is the primary beneficiary of the VIE. The Company’s only material asset is its ownership interest in the Operating Partnership, and consequently, all of its assets and liabilities represent those assets and liabilities of the Operating Partnership. The Company’s debt is an obligation of the Operating Partnership where the creditors may have recourse, under certain circumstances, against the credit of the Company.

Use of Estimates – The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Significant items subject to such estimates and assumptions include the useful lives of fixed assets, allowances for doubtful accounts and deferred tax assets and the valuation of derivatives, real estate assets, acquired intangible assets and certain accruals. The impacts of the COVID-19 pandemic increases uncertainty, which has reduced our ability to use past results to estimate future performance. Accordingly, our estimates and judgments may be subject to greater volatility than has been the case in the past.

We evaluate our investments in less than wholly owned entities to determine whether they should be recorded on a consolidated basis. The percentage of ownership interest in the entity, an evaluation of control and whether a VIE exists are all considered in our consolidation assessment. Investments in real estate entities which we have the ability to exercise significant influence, but do not have financial or operating control, are accounted for using the equity method of accounting. Accordingly, our share of the earnings or losses of these entities is included in consolidated net income (loss).

Variable Interest Entities (VIEs) – We determine whether an entity is a VIE and, if so, whether it should be consolidated by utilizing judgments and estimates that are inherently subjective. The determination of whether an entity in which we hold a direct or indirect variable interest is a VIE is based on several factors, including whether the entity’s total equity investment at risk upon inception is sufficient to finance the entity’s activities without additional subordinated financial support. We make judgments regarding the sufficiency of the equity at risk based first on a qualitative analysis, and then a quantitative analysis, if necessary.

We analyze any investments in VIEs to determine if we are the primary beneficiary. In evaluating whether we are the primary beneficiary, we evaluate our direct and indirect economic interests in the entity. Determining which reporting entity, if any, is the primary beneficiary of a VIE is primarily a qualitative approach focused on identifying which reporting entity has both (1) the power to direct the activities of a VIE that most significantly impact such entity’s economic performance and (2) the obligation to absorb losses or the right to receive benefits from such entity that could potentially be significant to such entity. Performance of that analysis requires the exercise of judgment.

We consider a variety of factors in identifying the entity that holds the power to direct matters that most significantly impact the VIE’s economic performance including, but not limited to, the ability to direct financing, leasing, construction and other operating decisions and activities. In addition, we consider the rights of other investors to participate in those decisions, to replace the manager and to sell or liquidate the entity. We determine whether we are the primary beneficiary of a VIE at the time we become involved with a variable interest entity and reconsider that conclusion upon a reconsideration event. As of March 31, 2021, we had one unconsolidated entity that was considered a VIE for which we are not the primary beneficiary. Our maximum exposure to losses associated with this VIE is limited to our net investment, which was approximately $25.9 million as of March 31, 2021.

Real Estate Assets – Real estate assets are reported at cost. All capital improvements for the income-producing properties that extend their useful lives are capitalized to individual property improvements and depreciated over their estimated useful lives. Depreciation for real estate assets is generally provided on a straight-line basis over 40 years from the date the property was placed in service. Property improvements are depreciated on a straight-line basis over the life of the respective improvement ranging from 20 to 40 years from the date the components were placed in service. Leasehold improvements are depreciated over the lesser of 20 years or through the end of the respective life of the lease. Repairs and maintenance costs are expensed as incurred. For the three months ended March 31, 2021, depreciation expense related to real estate assets and non-real estate assets was $42.7 million and $2.9 million, respectively, for a total of $45.6 million. For the three months ended March 31, 2020, depreciation expense related to real estate assets and non-real estate assets was $32.3 million and $3.4 million, respectively, for a total of $35.7 million. We capitalize certain real estate development costs, including internal costs incurred in connection with development. The capitalization of costs during the construction period (including interest and related loan fees, property taxes and other direct and indirect project costs) begins when development efforts commence and ends when the asset is ready for its intended use. The capitalization of internal costs increases construction in progress recognized during development of the related property and the cost of the real estate asset when placed into service and such costs are depreciated over its estimated useful life. Capitalization of such costs, excluding interest, aggregated to $5.5 million and $4.5 million for the three months ended March 31, 2021 and 2020, respectively. Interest is capitalized during the period of development by applying our weighted average effective borrowing rate to the actual development and other capitalized costs paid during the construction period. Interest is capitalized until the property is ready for its intended use. Interest costs capitalized totaled $7.0 million and $8.1 million for the three months ended March 31, 2021 and 2020, respectively.

Impairment of Long-Lived Assets, Intangible Assets and Goodwill – We review our long-lived assets, intangible assets and equity method investments for impairment when events or changes in circumstances indicate that the carrying amount of the assets may not be recoverable. Recoverability of assets to be held and used is measured by comparison of the carrying amount to the future net cash flows, undiscounted and without interest, expected to be generated by the asset group. If the net carrying value of the asset group exceeds the value of the undiscounted cash flows, the fair value of the asset group is assessed and may be considered impaired. An impairment loss is recognized based on the excess of the carrying amount of the impaired asset over its fair value. No impairment losses were recorded for the three months ended March 31, 2021 and March 31, 2020.

The fair value of goodwill is the consideration transferred in a business combination which is not allocable to identifiable intangible and tangible assets. Goodwill is subject to at least an annual assessment for impairment. In connection with the goodwill impairment evaluation that we performed as of October 1, 2020, we determined qualitatively that it is not more likely than not that the fair value of our one reporting unit was less than the carrying amount, thus we did not perform a quantitative analysis. As we continue to operate and assess our goodwill at the consolidated level for our single reporting unit and our market capitalization significantly exceeds our net asset value, further analysis was not deemed necessary as of March 31, 2021.

Cash and Cash Equivalents – We consider all demand deposits and money market accounts purchased with a maturity date of three months or less at the date of purchase to be cash equivalents. Our account balances at one or more institutions periodically exceed the Federal Deposit Insurance Corporation (“FDIC”) insurance coverage and, as a result, there is concentration of credit risk related to amounts on deposit in excess of FDIC coverage. We mitigate this risk by depositing a majority of our funds with several major financial institutions. We also have not experienced any losses and do not believe that the risk is significant.

Revenue Recognition – We derive our revenues from leases with customers for data center space which include lease components and nonlease revenue components, such as power, tenant recoveries, and managed services. We have elected the available practical expedient under ASC Topic 842, Leases, to combine our nonlease revenue components that have the same pattern of transfer as the related operating lease component into a single combined lease component. The single combined component is accounted for under ASC Topic 842 if the lease component is the predominant component and is accounted for under ASC Topic 606 if the nonlease components are the predominant components. In our contracts, the single combined component is accounted for under ASC Topic 842 as the lease component is the predominant component.

Rental revenue also includes revenue from power delivery on fixed power arrangements, whereby customers are billed and pay a fixed monthly fee per committed available amount of connected power. These fixed power arrangements require us to provide a series of distinct services and to stand ready to deliver the power over the contracted term which is co-terminus with the lease. Customer fixed power arrangements have the same pattern of transfer over the lease term as the lease component and are therefore combined with the lease component to form a single lease component that is recognized over the term of the lease on a straight-line basis.

In addition, rental revenue includes straight-line rent. Straight-line rent represents the difference in rents recognized during the period versus amounts contractually due pursuant to the underlying leases and is recorded as deferred rent receivable/payable in the consolidated balance sheets. For lease agreements that provide for scheduled rent increases, rental income is recognized on a straight-line basis over the non-cancellable term of the leases, which commences when control of the space has been provided to the customer. The amount of the straight-line rent receivable on the balance sheet included in rents and other receivables, net was $71.0 million and $63.6 million as of March 31, 2021 and December 31, 2020, respectively.

Certain customer leases contain provisions under which customers reimburse us for power and cooling-related charges as well as a portion of the property’s real estate taxes, insurance and other operating expenses. Recoveries of power and cooling-related expenses relate specifically to our variable power arrangements, whereby customers pay variable monthly fees for the specific amount of power utilized at the current utility rates. Our performance obligation is to stand ready to deliver power over the life of the customer contract up to a contracted power capacity. Customers have the flexibility to increase or decrease the amount of power consumed, and therefore sub-metered power revenue is constrained at contract inception. The reimbursements are included in revenue as recoveries from customers and are recognized each month as the uncertainty related to the consideration is resolved (i.e. we provide power to our customers) and customers utilize the power. Reimbursement of real estate taxes, insurance, common area maintenance, or other operating expenses are accounted for as variable payments under lease guidance pursuant to the practical expedient and are recognized as revenue in the period that the expenses are recognized. Variable lease revenue from recoveries discussed above, including power, common area maintenance or other operating costs, have the same pattern of transfer over the lease term as the lease component and are therefore combined with the lease component to form a single lease component. Variable lease revenue from recoveries is included within the “rental” line item on the statements of operations.

Other revenue primarily consists of revenue from our managed service offerings, as well as revenue earned from partner channel, management and development fees. We, through our taxable REIT subsidiaries (“TRS”), may provide use of our managed services to our customers on an individual or combined basis. In our managed services offering, the TRS’s performance obligation is to provide services (e.g. cloud hosting, data backup, data storage or data center personnel labor hours) to facilitate a fully integrated information technology (“IT”) outsourcing environment over a contracted term. Although underlying services may vary, over the contracted term monthly service offerings are substantially the same and we account for the services as a series of distinct services in accordance with ASC Topic 606. Service fee revenue is recognized as the revenue is earned, which generally coincides with the services being provided. As we have the right to consideration from customers in an amount that corresponds directly with the value to the customer of the TRS’s performance of providing continuous services, we recognize monthly revenue for the amount invoiced.

With respect to the transaction price allocated to remaining performance obligations within our managed service contracts, we have elected to use the optional exemption provided by ASC Topic 606 whereby we are not required to estimate the total transaction price allocated to remaining performance obligations as we apply the “right-to-invoice” practical expedient. As described above, the nature of our performance obligation in these contracts is to provide monthly services that are substantially the same and accounted for as a series of distinct services. These contracts generally have a remaining term ranging from month-to-month to three years.

Management fees and other revenues are generally received from our unconsolidated entity properties as well as third parties. Management fee revenue is earned based on a contractual percentage of unconsolidated entity property revenue. Development fee revenue is earned on a contractual percentage of hard costs to develop a property. We recognize revenue for these services provided when earned based on the performance criteria in ASC Topic 606, with such revenue recorded in “Other” revenue on the consolidated statements of operations.

Leases as Lessee – We determine if an arrangement is a lease at inception. If the contract is considered a lease, we evaluate leased property to determine whether the lease should be classified as a finance or operating lease in accordance with U.S. GAAP. We periodically enter into finance leases for certain data center facilities, equipment, and fiber optic transmission cabling. Finance lease assets are included within the “Buildings, improvements and equipment” line item of the consolidated balance sheets and finance lease liabilities are included within “Finance leases” line item of the consolidated balance sheets. In addition, we lease certain real estate (primarily land or real estate space) under operating lease agreements with such assets included within the “Operating lease right of use assets, net” line item of the consolidated balance sheets and the associated lease liabilities included within the “Operating lease liabilities” line item on the consolidated balance sheets.

Right of use (“ROU”) assets represent our right to use an underlying asset for the lease term and lease liabilities represent our obligation to make lease payments arising from the lease. ROU assets and lease liabilities are recognized at the commencement date based on the present value of lease payments over the lease term. Certain of our leases include variable payments, which may vary based upon changes in facts or circumstances after the start of the lease. Variable lease payments are excluded from the ROU assets and lease liabilities and are recognized in the period in which the obligation for those payments is incurred. As our leases as lessee typically do not provide an implicit rate, we use our incremental borrowing rate based on the information available at the commencement date in determining the present value of lease payments. We assess multiple variables when determining the incremental borrowing rate, such as lease term, payment terms, collateral, economic conditions, and creditworthiness. ROU assets also include any lease payments made and exclude lease incentives. Many of our lease agreements include options to extend the lease, which we do not include in our expected lease terms unless they are reasonably certain to be exercised. Rental expense for lease payments related to operating leases is recognized on a straight-line basis over the lease term.

Allowance for Uncollectible Accounts Receivable – We record a provision for uncollectible accounts if a receivable balance relating to lease components from an individual contract is considered by management not to be probable of collection, and this provision is recorded as a reduction to leasing revenues. We also record a general provision of estimated uncollectible tenant receivables based on general probability of collection in accordance with ASC 450-20 Loss Contingencies. This provision is recorded as bad debt expense and recorded within the “Property Operating Costs” line item of the consolidated statements of operations. The aggregate allowance for doubtful accounts on the consolidated balance sheets was $5.3 million and $5.4 million as of March 31, 2021 and December 31, 2020, respectively.

Deferred Income – Deferred income generally results from non-refundable charges paid by the customer at lease inception to prepare their space for occupancy. We record this initial payment, commonly referred to as set-up fees, as a deferred income liability which amortizes into rental revenue over the term of the related lease on a straight-line basis. Deferred income was $93.5 million and $85.4 million as of March 31, 2021 and December 31, 2020, respectively. Additionally, $6.4 million and $3.9 million of deferred income was amortized into revenue for the three months ended March 31, 2021 and 2020, respectively.

Income Taxes – We provide for income taxes during interim periods based on the estimated effective tax rate for the year and any discrete adjustments. The effective tax rate is subject to change in the future due to various factors such as the operating performance of the taxable REIT subsidiaries, tax law changes, and future business acquisitions or divestitures. The taxable subsidiaries’ effective tax rates were (7.8)% and 13.0% for the three months ended March 31, 2021 and 2020, respectively.

Fair Value Measurements – ASC Topic 820, Fair Value Measurement, emphasizes that fair value is a market-based measurement, not an entity-specific measurement. Therefore, a fair value measurement should be determined based on the assumptions that market participants would use in pricing the asset or liability. As a basis for considering market participant assumptions in fair value measurements, a fair value hierarchy is established that distinguishes between market participant assumptions based on market data obtained from sources independent of the reporting entity (observable inputs that are classified within Levels 1 and 2 of the hierarchy) and the reporting entity’s own assumptions about market participant assumptions (unobservable inputs classified within Level 3 of the hierarchy).

Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets or liabilities that we have the ability to access. Level 2 inputs are inputs other than quoted prices included in Level 1 that are observable for the asset or liability, either directly or indirectly. Level 2 inputs may include quoted prices for similar assets and liabilities in active markets, as well as inputs that are observable for the asset or liability (other than quoted prices), such as interest rates, foreign exchange rates, and yield curves that are observable at commonly quoted intervals. Level 3 inputs are unobservable inputs for the asset or liability, which are typically based on an entity’s own assumptions, as there is little, if any, related market activity. In instances where the determination of the fair value measurement is based on inputs from different levels of the fair value hierarchy, the level in the fair value hierarchy within which the entire fair value measurement falls is based on the lowest level input that is significant to the fair value measurement in its entirety. Our assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment, and considers factors specific to the asset or liability.

In January 2020, the FASB issued ASU 2020-1, Investments—Equity Securities (Topic 321), Investments—Equity Method and Joint Ventures (Topic 323), and Derivatives and Hedging (Topic 815): Clarifying the Interactions between Topic 321, Topic 323, and Topic 815, which clarifies the interaction between the accounting for equity securities under Topic 321, the accounting for equity method investments in Topic 323, and the accounting for certain forward contracts and purchased options in Topic 815. ASU 2020-1 is effective for fiscal years beginning after December 15, 2020, and interim periods within those fiscal years. We adopted this ASU effective January 1, 2021, and the provisions of the standard did not have a material impact on our consolidated financial statements.

In March 2020, the FASB issued ASU 2020-4, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting. ASU 2020-4 contains practical expedients for reference rate reform related activities that impact debt, leases, derivatives and other contracts. The guidance in ASU 2020-4 is optional and may be elected over time as reference rate reform activities occur. The standard is effective for all entities as of March 12, 2020 through December 31, 2022. An entity can elect to apply the amendments as of any date from the beginning of an interim period that includes or is subsequent to March 12, 2020, or prospectively from a date within an interim period that includes or is subsequent to March 12, 2020, up to that date that the financial statements are available to be issued. In January 2021, the FASB issued ASU 2021-1 Reference Rate Reform (Topic 848): Scope, which updated the standard to clarify that certain optional expedients and exceptions in Topic 848 for contract modifications and hedge accounting apply to derivatives that are affected by the discounting transition. Beginning in the first quarter of 2020, we have applied the hedge accounting expedients related to probability and the assessments of effectiveness for future LIBOR-indexed cash flows to assume that the index upon which future hedged transactions will be based matches the index on the corresponding derivatives. Application of these expedients preserves the presentation of derivatives consistent with past presentation. We continue to evaluate the impact of the guidance but we do not expect the provisions of the standard will have a material impact on our consolidated financial statements.