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Organization and Significant Accounting Policies | 12 Months Ended
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Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract] |
Organization and Significant Accounting Policies |
1. Organization and Significant Accounting Policies
Organization and Business
DexCom, Inc. is a medical device company that develops and markets continuous glucose monitoring, or CGM, systems for the management of diabetes by patients, caregivers, and clinicians around the world. Unless the context requires otherwise, the terms “we,” “us,” “our,” the “company,” or “Dexcom” refer to DexCom, Inc. and its subsidiaries.
Basis of Presentation and Principles of Consolidation
These consolidated financial statements include the accounts of DexCom, Inc. and our wholly owned subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation. We have reclassified certain amounts previously reported in our financial statements to conform to the current presentation. We determine the functional currencies of our international subsidiaries by reviewing the environment where each subsidiary primarily generates and expends cash. For international subsidiaries whose functional currencies are the local currencies, we translate the financial statements into U.S. dollars using period-end exchange rates for assets and liabilities and average exchange rates for each period for revenue, costs and expenses. We include translation-related adjustments in comprehensive income and in accumulated other comprehensive income in the equity section of our consolidated balance sheets. We record gains and losses resulting from transactions with customers and vendors that are denominated in currencies other than the functional currency and from certain intercompany transactions in interest and other income (expense), net in our consolidated statements of operations.
Use of Estimates
The preparation of consolidated financial statements in conformity with U.S. generally accepted accounting principles, or GAAP, requires us to make certain estimates and assumptions that affect the amounts reported in our consolidated financial statements and the disclosures made in the accompanying notes. Areas requiring significant estimates include rebates, transaction price, the collectibility of accounts receivable, excess or obsolete inventories and the valuation of inventory, accruals for litigation contingencies, and the amount of our worldwide tax provision and the realizability of deferred tax assets. Despite our intention to establish accurate estimates and use reasonable assumptions, actual results may differ from our estimates.
Fair Value Measurements
The authoritative guidance establishes a fair value hierarchy that is based on the extent and level of judgment used to estimate the fair value of assets and liabilities. In general, the authoritative guidance requires us to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. An asset or liability’s categorization within the fair value hierarchy is based upon the lowest level of input that is significant to the measurement of its fair value. The three levels of input defined by the authoritative guidance are as follows: Level 1—Uses unadjusted quoted prices that are available in active markets for identical assets or liabilities. Level 2—Uses inputs other than quoted prices included in Level 1 that are observable, either directly or indirectly, through correlation with market data. These include quoted prices in active markets for similar assets or liabilities; quoted prices for identical or similar assets or liabilities in markets that are not active; and inputs to valuation models or other pricing methodologies that do not require significant judgment because the inputs used in the model, such as interest rates and volatility, can be corroborated by readily observable market data for substantially the full term of the assets or liabilities. Level 3—Uses unobservable inputs that are supported by little or no market activity and that are significant to the determination of fair value. Level 3 assets and liabilities include those whose fair values are determined using pricing models, discounted cash flow methodologies, or similar valuation techniques and significant judgment or estimation. We estimate the fair value of most of our cash equivalents using Level 1 inputs. We estimate the fair value of our marketable equity securities using Level 1 inputs and we estimate the fair value of our marketable debt securities using Level 2 inputs. We carry our marketable securities at fair value. We carry our other financial instruments, such as cash and cash equivalents, accounts receivable, prepaid expenses and other current assets, accounts payable and accrued liabilities, at cost, which approximates the related fair values due to the short-term maturities of these instruments. See Note 3 “Fair Value Measurements” for more information.
Cash and Cash Equivalents
We consider highly liquid investments with a maturity of 90 days or less at the time of purchase to be cash equivalents.
Marketable Securities
We have classified our marketable securities with remaining maturity at purchase of more than three months and remaining maturities of one year or less as short-term marketable securities. We have also classified marketable securities with remaining maturities of greater than one year as short-term marketable securities based upon our ability and intent to use any and all of those marketable securities to satisfy the liquidity needs of our current operations. We calculate realized gains or losses on our marketable securities using the specific identification method. We carry our marketable debt securities at fair value with unrealized gains and losses reported as a separate component of stockholders’ equity in our consolidated balance sheets and included in comprehensive income. Realized gains and losses on marketable debt securities are included in interest and other income (expense), net in our consolidated statements of operations. We carry our marketable equity securities at fair value with realized and unrealized gains and losses reported in income (loss) from equity investments in our consolidated statements of operations. We invest in various types of debt securities, including debt securities in government-sponsored entities, corporate debt securities, U.S. Treasury securities, supranational securities, and commercial paper. We do not generally intend to sell these investments and it is not more likely than not that we will be required to sell the investments before recovery of their amortized cost bases, which may be at maturity. See Note 3 “Fair Value Measurements” and Short-Term Marketable Securities in Note 4 “Balance Sheet Details” for more information on our marketable securities.
Accounts Receivable and Allowance for Doubtful Accounts
Accounts receivable are generally recorded at the invoiced amount, net of prompt pay discounts, for distributors and at net realizable value for direct customers, which is determined using estimates of claim denials and historical reimbursement experience without regard to aging category. Accounts receivable are not interest bearing. We evaluate the creditworthiness of significant customers based on historical trends, the financial condition of our customers, and external market factors. We generally do not require collateral from our customers. We maintain an allowance for doubtful accounts for potential credit losses. Uncollectible accounts are written off against the allowance after appropriate collection efforts have been exhausted and when it is deemed that a customer account is uncollectible. Generally, receivable balances greater than one year past due are deemed uncollectible.
Concentration of Credit Risk and Significant Customers
Financial instruments which potentially subject us to concentrations of credit risk consist primarily of cash, cash equivalents, short-term marketable securities, and accounts receivable. We limit our exposure to credit risk by placing our cash and investments with a few major financial institutions. We have also established guidelines regarding diversification of our investments and their maturities that are designed to maintain principal and maximize liquidity. We review these guidelines periodically and modify them to take advantage of trends in yields and interest rates and changes in our operations and financial position. The following table sets forth the percentages of total revenue or gross accounts receivable for customers that represent 10% or more of the respective amounts for the periods shown:
| Revenue |  | Gross Accounts Receivable
| Twelve Months Ended December 31, |  | As of December 31,
| 2021 |  | 2020 |  | 2019 |  | 2021 |  | 2020
Distributor A | 28 | % |  | 23 | % |  | 17 | % |  | 16 | % |  | 19 | %
Distributor B | 12 | % |  | 11 | % |  | 12 | % |  | 11 | % |  | 10 | %
Distributor C | 21 | % |  | 18 | % |  | 10 | % |  | 13 | % |  | 12 | %
Distributor D | 18 | % |  | 11 | % |  | * |  | 13 | % |  | *
* Less than 10%
Inventory
Inventory is valued at the lower of cost or net realizable value on a part-by-part basis that approximates first in, first out. We capitalize inventory produced in preparation for commercial launches when it becomes probable that the product will receive regulatory approval and that the related costs will be recoverable through the commercialization of the product. A number of factors are considered, including the status of the regulatory application approval process, management’s judgment of probable future commercial use, and net realizable value. We record adjustments to inventory for potential excess or obsolete inventory, as well as inventory that does not pass quality control testing, in order to state inventory at net realizable value. Factors influencing these adjustments include inventories on hand and on order compared to estimated future usage and sales for existing and new products, as well as judgments regarding quality control testing data and assumptions about the likelihood of scrap and obsolescence. Once written down the adjustments are considered permanent and are not reversed until the related inventory is sold or disposed of. Our products require customized products and components that currently are available from a limited number of sources. We purchase certain components and materials from single sources due to quality considerations, costs or constraints resulting from regulatory requirements. Historically, our inventory reserves have been adequate to cover our actual losses. However, if actual product life cycles, product quality or market conditions differ from our assumptions, additional inventory adjustments that would increase cost of goods sold could be required.
Property and Equipment
Property and equipment is stated at cost less accumulated depreciation and amortization. We capitalize additions and improvements and expense maintenance and repairs as incurred. We also capitalize certain costs incurred for the development of enterprise-level business and finance software that we use internally in our operations. Costs incurred in the application development phase are capitalized while costs related to planning and other preliminary project activities and to post-implementation activities are expensed as incurred. We calculate depreciation using the straight-line method over the estimated useful lives of the assets. Estimated useful lives are generally three years for computer software and hardware, including internal use software, four to fifteen years for machinery and equipment, and five years for furniture and fixtures. Leasehold improvements are amortized over the shorter of the estimated useful lives of the assets or the remaining lease term. Buildings are amortized over the shorter of the ownership of the building or forty years. We include the amortization of assets that are recorded under finance leases in depreciation expense. On retirement or disposition, the asset cost and related accumulated depreciation are removed from our consolidated balance sheets and any gain or loss is recognized in our consolidated statements of operations. We review property and equipment for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. We estimate the recoverability of the asset by comparing the carrying amount to the future undiscounted cash flows that we expect the asset to generate. We estimate the fair value of the asset based on the present value of future cash flows for those assets. If the carrying value of an asset exceeds its estimated fair value, we would record an impairment loss equal to the difference.
Goodwill
We record goodwill when the fair value of consideration transferred in a business combination exceeds the fair value of the identifiable assets acquired and liabilities assumed. Goodwill and other intangible assets that have indefinite useful lives are not amortized, but we test them annually for impairment in the fourth quarter of our fiscal year and whenever events or changes in circumstances indicate that it is more likely than not that the fair value is less than the carrying value. Events that would indicate impairment and trigger an interim impairment assessment include, but are not limited to, current economic and market conditions, including a decline in market capitalization, a significant adverse change in legal factors, business climate or operational performance of the business, and an adverse action or assessment by a regulator. We perform our goodwill impairment analysis at the reporting unit level, which aligns with Dexcom’s reporting structure and the availability of discrete financial information. We perform the first step of our annual impairment analysis by either comparing a reporting unit’s estimated fair value to its carrying amount or doing a qualitative assessment of a reporting unit’s fair value from the last quantitative assessment to determine if there is potential impairment. We may do a qualitative assessment when the results of the previous quantitative test indicated the reporting unit’s estimated fair value was significantly in excess of the carrying value of its net assets and we do not believe there have been significant changes in the reporting unit’s operations that would significantly decrease its estimated fair value or significantly increase its net assets. If a quantitative assessment is performed the evaluation includes management estimates of cash flow projections based on internal future projections and/or use of a market approach by looking at market values of comparable companies. Key assumptions for these projections include revenue growth, future gross margin and operating margin growth, and weighted cost of capital and terminal growth rates. The revenue and margin growth are based on increased sales of new and existing products as we maintain investments in research and development. Additional assumed value creators may include increased efficiencies from capital spending. The resulting cash flows are discounted using a weighted average cost of capital. Operating mechanisms and requirements to ensure that growth and efficiency assumptions will ultimately be realized are also considered in the evaluation, including the timing and probability of regulatory approvals for our products to be commercialized. We also consider Dexcom’s market capitalization as a part of our analysis. If the estimated fair value of a reporting unit exceeds the carrying amount of the net assets assigned to that unit, goodwill is not impaired and no further analysis is required. If the carrying value of the net assets assigned to a reporting unit exceeds the estimated fair value of the unit, we perform the second step of the impairment test. In this step we allocate the fair value of the reporting unit calculated in step one to all of the assets and liabilities of that unit, as if we had just acquired the reporting unit in a business combination. The excess of the fair value of the reporting unit over the total amount allocated to the assets and liabilities represents the implied fair value of goodwill. If the carrying amount of a reporting unit’s goodwill exceeds its implied fair value, we would record an impairment loss equal to the difference. We recorded no goodwill impairment charges for the twelve months ended December 31, 2021, 2020 or 2019. The change in goodwill for the twelve months ended December 31, 2021 consisted of goodwill we recorded for acquisitions that were not significant, individually or in the aggregate, and translation adjustments on our foreign currency denominated goodwill. The change in goodwill for the twelve months ended December 31, 2020 and 2019 consisted of translation adjustments on our foreign currency denominated goodwill.
Intangible Assets and Other Long-Lived Assets
Intangible assets are included in intangibles and other assets, net in our consolidated balance sheets. We amortize intangible assets with a finite life, such as acquired technology, customer relationships, trade names and trademarks, on a straight-line basis over their estimated useful lives, which range from one to seven years. We review intangible assets that have finite lives and other long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. We estimate the fair value of the asset based on the present value of future cash flows for those assets. If the carrying value of an asset exceeds its estimated fair value, we would record an impairment loss equal to the difference. For transactions other than a business combination, we also capitalize as intangible assets the cost of certain milestones payable by us to collaborative partners and incurred at or after the product has obtained regulatory approval for marketing. The intangible assets associated with these milestones are amortized over the remaining estimated useful life of the underlying asset. We recorded no intangible asset impairment charges for the twelve months ended December 31, 2021, 2020 or 2019.
Income Taxes
We account for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. The effect of a change in tax rate on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. We recognize deferred tax assets to the extent that we believe that these assets are more likely than not to be realized. In making such determination, we consider all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, carryback potential if permitted under tax law and results of recent operations. If we determine that we would be able to realize our deferred tax assets in the future in excess of their net recorded amount, we would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes. We record uncertain tax positions in accordance with ASC 740 on the basis of a two-step process in which (1) we determine whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (2) for those tax positions that meet the more-likely-than-not recognition threshold, we recognize the largest amount of tax benefit that is more than 50 percent likely to be realized upon ultimate settlement with the related tax authority. We file federal and state income tax returns in the United States and income tax returns in various other foreign jurisdictions with varying statutes of limitations. Due to net operating losses incurred, our income tax returns from inception to date are subject to examination by taxing authorities. We recognize interest expense and penalties related to income tax matters, including unrecognized tax benefits, as a component of income tax expense.
Warranty Accrual
Estimated warranty costs associated with a product are recorded at the time revenue is recognized. We estimate future warranty costs by analyzing historical warranty experience for the timing and amount of returned product, and expectations for future warranty activity based on changes and improvements to the product or process that are in place or will be in place in the future. We evaluate these estimates on at least a quarterly basis to determine the continued appropriateness of our assumptions.
Loss Contingencies
We are subject to certain legal proceedings, as well as demands, claims and threatened litigation that arise in the normal course of our business. We review the status of each significant matter quarterly and assess our potential financial exposure. If the potential loss from a claim or legal proceeding is considered probable and the amount can be reasonably estimated, we record a liability and an expense for the estimated loss and disclose it in our financial statements if it is significant. If we determine that a loss is possible and the range of the loss can be reasonably determined,we do not record a liability or an expense but we disclose the range of the possible loss. We base our judgments on the best information available at the time. As additional information becomes available, we reassess the potential liability related to our pending claims and litigation and may revise our estimates. Any revision of our estimates of potential liability could have a material impact on our financial position and operating results.
Comprehensive Income
Comprehensive income consists of two elements, net income and other comprehensive income (loss). We report all components of comprehensive income, including net income, in our financial statements in the period in which they are recognized. Total comprehensive income is defined as the change in equity during a period from transactions and other events and circumstances from non-owner sources. We report net income and the components of other comprehensive income (loss), including foreign currency translation adjustments and unrealized gains and losses on marketable securities, net of their related tax effect to arrive at total comprehensive income.
Revenue Recognition
We generate our revenue from the sale of disposable sensors and our reusable transmitter and receiver, collectively referred to as Reusable Hardware. We also refer to Reusable Hardware and disposable sensors in this section as Components. We generally recognize revenue when control is transferred to our customers in an amount that reflects the net consideration to which we expect to be entitled. In determining how revenue should be recognized, a five-step process is used, which includes identifying performance obligations in the contract, determining whether the performance obligations are separate, allocating the transaction price to each separate performance obligation, estimating the amount of variable consideration to include in the transaction price and determining the timing of revenue recognition for separate performance obligations. Contracts and Performance Obligations We consider customer purchase orders, which in most cases are governed by agreements with distributors or third-party payors, to be contracts with a customer. For each contract, we consider the obligation to transfer Components to the customer, each of which are distinct, to be separate performance obligations. We also provide free-of-charge software, mobile applications and updates for our Dexcom Share® remote monitoring system. The standalone selling prices of Dexcom Share® are estimated based on an expected cost plus a margin approach. Transaction Price Transaction price for the Components reflects the net consideration to which we expect to be entitled. Transaction price is typically based on the contracted rates less an estimate of claim denials and historical reimbursement experience by payor, which include current and future expectations regarding reimbursement rates and payor mix. Variable Consideration We include an estimate of variable consideration in the calculation of the transaction price at the time of sale, when control of the Components transfers to the customer. Variable consideration includes but is not limited to: rebates, chargebacks, consideration payable to customers such as specialty distributor and wholesaler fees, product returns provision, prompt payment discounts, and various other promotional or incentive arrangements. We classify our provisions related to variable consideration as a reduction of accounts receivable when we are not required to make a payment or as a liability when we are required to make a payment. Estimates We review the adequacy of our estimates for transaction price adjustments and variable consideration at each reporting date. If the actual amounts of consideration that we receive differ from our estimates, we would adjust our estimates and that would affect reported revenue in the period that such variances become known. If any of these judgments were to change, it could cause a material increase or decrease in the amount of revenue we report in a particular period. Rebates We are subject to rebates on pricing programs with managed care organizations, such as pharmacy benefit managers, governmental and third-party commercial payors, primarily in the U.S. We estimate provisions for rebates based on contractual arrangements, estimates of products sold subject to rebate, known events or trends, and channel inventory data. Chargebacks We participate in chargeback programs, primarily with government entities in the U.S., under which pricing on products below negotiated list prices is provided to participating entities and equal to the difference between their acquisition cost and the lower negotiated price. We estimate provisions for chargebacks primarily based on historical experience on a product and program basis, current contract prices under the chargeback programs, and channel inventory data. Consideration Payable to the Customer We pay administrative and service fees to certain of our distributors based on a fixed percentage of the product price. These fees are not in exchange for a distinct good or service and therefore are recognized as a reduction of the transaction price. We accrue for these fees based on actual net sales and contractual fee rates negotiated with the customer. Product Returns In accordance with the terms of their distribution agreements, most distributors do not have rights of return. The distributors typically have a limited time frame to notify us of any missing, damaged, defective or non-conforming products. We generally provide a “30-day money back guarantee” program whereby first-time end-user customers may return Reusable Hardware. We estimate our product returns provision principally based on historical experience by applying a historical return rate to the amounts of revenue estimated to be subject to returns. Additionally, we consider other specific factors such as estimated shelf life of inventory in the distribution channel and changes to customer terms. Prompt Payment Discounts We provide customers with prompt payment discounts which may result in adjustments to the price that is invoiced for the product transferred, in the case that payments are made within a defined period. We estimate prompt payment discount accruals based on actual net sales and contractual discount rates. Various Other Promotional or Incentive Arrangements Other promotional or incentive arrangements are periodically offered to customers, including but not limited to co-payment assistance we provide to patients with commercial insurance, promotional programs related to the launch of products, or other targeted promotions. We record a provision for the incentive earned based on the number of estimated claims and our estimate of the cost per claim related to product sales that we have recognized as revenue. Revenue Recognition The timing of revenue recognition is based on the satisfaction of performance obligations. Substantially all of the performance obligations associated with our Components are satisfied at a point in time, which typically occurs at shipment of our products. Terms of direct and distributor orders are generally Freight on Board (FOB) shipping point for U.S. orders or Free Carrier (FCA) shipping point for international orders. For certain sales transactions, control transfers at delivery of the product to the customer. In cases where our free-of-charge software, mobile applications and updates are deemed to be separate performance obligations, revenue is recognized over time on a ratable basis over the estimated life of the related Reusable Hardware component. Our sales of Components include an assurance-type warranty. Contract Balances Contract balances represent amounts presented in our consolidated balance sheets when either we have transferred goods or services to the customer or the customer has paid consideration to us under the contract. These contract balances include accounts receivable and deferred revenue. Payment terms vary by contract type and type of customer and generally range from 30 to 90 days. Accounts receivable as of December 31, 2021 included unbilled accounts receivable of $9.6 million. We expect to invoice and collect all unbilled accounts receivable within twelve months. We record deferred revenue when we have entered into a contract with a customer and cash payments are received or due prior to transfer of control or satisfaction of the related performance obligation. Our performance obligations are generally satisfied within 12 months of the initial contract date. The deferred revenue balances related to performance obligations that will be satisfied after 12 months was $16.1 million as of December 31, 2021 and $8.2 million as of December 31, 2020. These balances are included in other long-term liabilities in our consolidated balance sheets. Revenue recognized in the period from performance obligations satisfied in previous periods was not material for the periods presented. Deferred Cost of Sales Deferred cost of sales are associated with transactions for which revenue recognition criteria are not met but product has shipped and released from inventory. Deferred cost of sales are included in prepaid and other current assets in our consolidated balance sheets. Incentive Compensation Costs We generally expense incentive compensation associated with our internal sales force when incurred because the amortization period for such costs, if capitalized, would have been one year or less. We record these costs in selling, general and administrative expense in our consolidated statements of operations.
Product Shipment Costs
We record the amounts we charge our customers for the shipping and handling of our products in revenue and we record the related costs as cost of sales in our consolidated statements of operations.
Research and Development
We expense costs of research and development as we incur them. Our research and development expenses primarily consist of engineering and research expenses related to our continuous glucose monitoring technology, clinical trials, regulatory expenses, quality assurance programs, materials and products for clinical trials. Research and development expenses primarily consist of employee compensation, including salary, fringe benefits, share-based compensation, and temporary employee expenses. We also incur significant expenses to operate our clinical trials that include clinical site reimbursement, clinical trial product, and associated travel expenses. Our research and development expenses also include fees for design services, contractors, and development materials. Our CGM systems include certain software that we develop. We expense software development costs as we incur them until technological feasibility has been established, at which time we capitalize development costs until the product is available for general release to customers. To date, our software has been available for general release concurrent with the establishment of technological feasibility and, accordingly, we have not capitalized any development costs.
Collaboration Agreements
We may enter into agreements with collaboration partners for the development and commercialization of our products. These arrangements may include payments contingent on the occurrence of certain events such as development, regulatory or sales-based milestones. When we account for these agreements, we consider the unique nature, terms and facts and circumstances of each transaction. Below are some example activities and how we account for them: •Payments to collaboration partners through issuance of common stock as consideration in an asset acquisition are considered share-based payment to non-employees in exchange for goods within the scope of ASC Topic 718, “Compensation - Stock Compensation”. The amount and the timing of the cost recognition of such milestones in our financial statements is driven by the accounting for the specific type of equity instrument under ASC 718 that aligns with the terms of the agreement, including any performance conditions. •The value associated with in-process research and development (“IPR&D”) in an asset acquisition incurred prior to regulatory approval is expensed as it does not have an alternative future use and is recorded as research and development expense. •The value associated with IPR&D in an asset acquisition incurred at or after regulatory approval is usually capitalized as an intangible asset and amortized over the periods in which the related products are expected to contribute to future cash flows.
Advertising Costs
We expense costs to produce advertising as we incur them whereas costs to communicate advertising are expensed when the advertising is first run. Advertising costs are included in selling, general and administrative expenses. Advertising expense was $126.4 million, $76.5 million and $33.1 million for the twelve months ended December 31, 2021, 2020 and 2019, respectively.
Leases
We determine if an arrangement is a lease at inception. Lease right-of-use 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. Operating lease right-of-use assets and liabilities are recognized at commencement date based on the present value of lease payments over the lease term. The interest rate used to determine the present value of the future lease payments is our incremental borrowing rate, because the interest rate implicit in most of our leases is not readily determinable. Our incremental borrowing rate is estimated to approximate the interest rate on a collateralized basis with similar terms and payments, and in similar economic environments. The operating lease right-of-use asset also includes any lease payments made and excludes lease incentives. We have lease agreements with lease and non-lease components, which are generally accounted for separately. Our lease terms may include options to extend or terminate the lease when it is reasonably certain that we will exercise that option. Lease expense for lease payments is recognized on a straight-line basis over the lease term. Variable lease payments that do not depend on a rate or index, payments associated with non-lease components, and costs related to leases with terms of less than 12 months are expensed as incurred.
Share-Based Compensation
Share-based compensation expense is measured at the grant date based on the estimated fair value of the award and is recognized straight-line over the requisite service period of the individual grants, which typically equals the vesting period. We value time-based restricted stock units or RSUs at the date of grant using the intrinsic value method. Certain RSUs granted to senior management vest based on the achievement of pre-established performance or market goals. We estimate the fair value of performance/market-based RSUs at the date of grant using the intrinsic value method and the probability that the specified performance criteria will be met. We update our assessment of the probability that the specified performance criteria will be achieved each quarter and adjust our estimate of the fair value of the performance-based RSUs if necessary. The Monte Carlo methodology that we use to estimate the fair value of market-based RSUs at the date of grant incorporates into the valuation the possibility that the market condition may not be satisfied. Provided that the requisite service is rendered, the total fair value of the market-based RSUs at the date of grant must be recognized as compensation expense even if the market condition is not achieved. However, the number of shares that ultimately vest can vary significantly with the performance of the specified market criteria. If any of the assumptions used change significantly, share-based compensation expense may differ materially from what we have recorded in the current period. We account for forfeitures as they occur by reversing any share-based compensation expense related to awards that will not vest.
Net Income Per Share
Basic net income per share attributable to common stockholders is calculated by dividing the net income attributable to common stockholders by the weighted-average number of common shares outstanding during the period. Diluted net income per share is computed using the weighted average number of common shares outstanding during the period and, when dilutive, potential common share equivalents. Potentially dilutive common shares consist of shares issuable from restricted stock units, warrants and our senior convertible notes. Potentially dilutive common shares issuable upon vesting of restricted stock units and exercise of warrants are determined using the average share price for each period under the treasury stock method. Potentially dilutive common shares issuable upon conversion of our senior convertible notes are determined using the if-converted method. In periods of net losses, we exclude all potentially dilutive common shares from the computation of the diluted net loss per share for those periods as the effect would be anti-dilutive. The following table sets forth the computation of basic and diluted net income per share for the periods shown.
|  | Twelve Months Ended December 31,
(In millions) |  | 2021 |  | 2020 |  | 2019
Net income |  | $ | 154.7 |  |  | $ | 493.6 |  |  | $ | 101.1 |
Net income per common share |  |  |  |  |  |
Basic |  | $ | 1.60 |  |  | $ | 5.23 |  |  | $ | 1.11 |
Diluted |  | $ | 1.55 |  |  | $ | 5.06 |  |  | $ | 1.10 |
Basic weighted average shares outstanding |  | 96.7 |  |  | 94.4 |  |  | 91.1 |
Dilutive potential common stock outstanding: |  |  |  |  |  |
Restricted stock units |  | 0.5 |  |  | 1.0 |  |  | 1.2 |
Warrants |  | 2.9 |  |  | 2.1 |  |  | — |
Diluted weighted average shares outstanding |  | 100.1 |  |  | 97.5 |  |  | 92.3 |
Outstanding anti-dilutive securities not included in the diluted net income per share attributable to common stockholders calculations were as follows:
| Twelve Months Ended December 31,
(In millions) | 2021 |  | 2020 |  | 2019
Restricted stock units | — |  |  | — |  |  | 0.2 |
Warrants | — |  |  | — |  |  | 5.2 |
Senior convertible notes | 6.8 |  |  | 7.2 |  |  | 9.2 |
Total | 6.8 |  |  | 7.2 |  |  | 14.6 |
Recent Accounting Guidance
Recently Adopted Accounting Pronouncements In December 2019, the FASB issued ASU No. 2019-12, Simplifying the Accounting for Income Taxes, which is intended to simplify various aspects of the income tax accounting guidance, including requirements such as tax basis step-up in goodwill obtained in a transaction that is not a business combination, ownership changes in investments, and interim-period accounting for enacted changes in tax law. ASU 2019-12 is effective for public business entities for fiscal years beginning after December 15, 2020, including interim periods within those fiscal years, and early adoption is permitted. Our adoption of ASU 2019-12 at the beginning of the first quarter of 2021 did not have a significant impact on our consolidated financial statements. Recently Issued Accounting Pronouncements Not Yet Adopted In August 2020, the FASB issued ASU No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40). This new guidance is intended to reduce the complexity of accounting for convertible instruments. The guidance also addresses how convertible instruments are accounted for in the diluted earnings per share calculation and requires enhanced disclosures about the terms of convertible instruments. Entities may adopt ASU 2020-06 using either a partial retrospective or fully retrospective method of transition. This ASU is effective for public business entities for fiscal years beginning after December 15, 2021, including interim periods within those fiscal years. Early adoption is permitted for fiscal years beginning after December 15, 2020, including interim periods within those fiscal years. We will adopt ASU 2020-06 in the first quarter of 2022, and expect to use the full retrospective method, reflecting the application of the new standard in each prior reporting period. We have started the process of evaluating the impact of the full retrospective adoption of ASU 2020-06 on our consolidated financial statements. We continue to evaluate the effect of ASU 2020-06 on our consolidated financial statements. Under ASU 2020-06, we will account for our senior convertible notes entirely as a liability and will no longer separately account for them with liability and equity components. Therefore, we will no longer recognize a debt discount for the value of the conversion option, instead we will record the face value of our senior convertible notes as a liability on our consolidated balance sheet. The derecognition of the unamortized debt discount will result in an increase in the Long-term senior convertible notes on our consolidated balance sheet. The elimination of the separation model for the convertible debt instruments is expected to reduce additional paid-in capital. As the separation of the embedded conversion feature will no longer be amortized into income as interest expense, non-cash interest expense will decrease by the full amount of the previous accretion of debt discount, offset by incremental interest expense from amortization of debt issuance costs that were allocated to the equity component. We will finalize our retrospective presentation of our historical financial statements under the new standard in connection with our Form 10-Q filings during fiscal year 2022 and our Form 10-K for the fiscal year ending December 31, 2022. In October 2021, the FASB issued ASU No. 2021-08, Business Combinations (Topic 805): Accounting for Contract Assets and Contract Liabilities from Contracts with Customers. This guidance is intended improve the accounting for acquired revenue contracts with customers in a business combination. The new guidance requires that the acquirer recognize and measure contract assets and contract liabilities acquired in a business combination in accordance with Topic 606. ASU 2021-08 is effective for public business entities for fiscal years beginning after December 15, 2022, including interim periods within those fiscal years, and early adoption is permitted. The amendments should be applied prospectively to business combinations occurring on or after the the adoption date. We are currently evaluating the impact that this guidance will have on our consolidated financial statements.

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