SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
Dec. 31, 2020
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Principles of Consolidation The consolidated financial statements include the accounts of all entities controlled by the Company through its direct or indirect ownership of a majority voting interest. Additionally, the consolidated financial statements include the accounts of variable interest entities (“VIEs”) in which the Company has a variable interest and for which the Company is the “primary beneficiary” as it has both: (1) the power to direct the activities of the VIE that most significantly impact the VIE’s economic performance and (2) the obligation to absorb losses of the VIE that potentially could be significant to the VIE or the right to receive benefits from the VIE that potentially could be significant to the VIE. All significant intercompany accounts and transactions are eliminated in consolidation. Income attributable to the minority interest in the Company's majority owned and controlled consolidated subsidiaries is recorded as net income attributable to noncontrolling interests in the consolidated statements of operations and the noncontrolling interest is reflected as a separate component of consolidated stockholders' equity in the consolidated balance sheet. Basis of Presentation During the third quarter of 2006, the Company completed the wind down of Nichols Institute Diagnostics ("NID"), a test kit manufacturing subsidiary. The accompanying consolidated statements of operations and related disclosures report the results of NID as discontinued operations through 2019, at which point certain income tax contingencies related to NID were resolved. See Note 21 for a further discussion of discontinued operations. Reclassifications Certain amounts in the prior period financial statements have been reclassified to conform to the presentation of the current period financial statements. Equity Method Investments Investments in entities which the Company does not control, but in which it has a substantial ownership interest (generally between 20% and 49%) and can exercise significant influence, are accounted for using the equity method of accounting. These investments are classified as investments in equity method investees in the consolidated balance sheet. The Company records its pro rata share of the earnings, adjusted for accretion of basis difference, of these investments in equity in earnings of equity method investees, net of taxes in the consolidated statements of operations. The Company reviews its investments in equity method investees for impairment whenever events or changes in circumstances indicate that the carrying amounts may not be recoverable. Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States (“GAAP”) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and 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. Revenue Recognition The Company recognizes as revenue the amount that reflects the consideration to which it expects to be entitled in exchange for goods sold or services rendered primarily upon completion of the testing process (when results are reported) or when services have been rendered (see Note 3). Net revenues from Medicare and Medicaid programs were approximately 11%, 15% and 16% of the Company's consolidated net revenues for the years ended December 31, 2020, 2019 and 2018, respectively. Taxes on Income The provision for income taxes represents income taxes paid or payable for the current year plus the change in deferred taxes during the year. Current and deferred income taxes are measured based on the tax laws that are enacted as of the balance sheet date of the relevant reporting period. Deferred tax assets and liabilities are recognized for the expected future tax consequences of differences between the carrying amounts of assets and liabilities and their respective tax bases using tax rates in effect for the year in which the differences are expected to reverse. A valuation allowance is provided when it is more likely than not that some portion or all of the deferred tax assets will not be realized. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period when the change is enacted. Tax benefits from uncertain tax positions are recognized only if the tax position is more likely than not to be sustained upon examination by taxing authorities based on the technical merits of the position. Earnings Per Share The Company's unvested restricted stock units that contain non-forfeitable rights to dividends are participating securities and, therefore, are included in the earnings allocation in computing earnings per share using the two-class method. Basic earnings per common share is calculated by dividing net income attributable to Quest Diagnostics, adjusted for earnings allocated to participating securities, by the weighted average number of common shares outstanding. Diluted earnings per common share is calculated by dividing net income attributable to Quest Diagnostics, adjusted for earnings allocated to participating securities, by the weighted average number of common shares outstanding after giving effect to all potentially dilutive common shares outstanding during the period. Potentially dilutive common shares include the dilutive effect of outstanding stock options and performance share units granted under the Company's Amended and Restated Employee Long-Term Incentive Plan (“ELTIP”) and its Amended and Restated Non-Employee Director Long-Term Incentive Plan (“DLTIP”). Earnings allocable to participating securities include the portion of dividends declared as well as the portion of undistributed earnings during the period allocable to participating securities. Stock-Based Compensation The Company measures stock-based compensation for equity awards at fair value on the date of grant and records stock-based compensation as a charge to earnings net of the estimated impact of forfeited awards. As such, the Company recognizes stock-based compensation cost only for those stock-based awards that are estimated to ultimately vest over their requisite service period, based on the vesting provisions of the individual grants. The cumulative effect on current and prior periods of a change in the estimated forfeiture rate is recognized as compensation cost in earnings in the period of the change. The terms of the Company's performance share units allow the recipients of such awards to earn a variable number of shares based on the achievement of the performance goals, which are based on the financial performance of the Company and the total shareholder return of the Company relative to an index of peer companies ("relative TSR"), specified in the awards. For performance share units with a goal based on the financial performance of the Company, stock-based compensation expense is recognized based on management's best estimates of the achievement of the performance goals specified in such awards and the resulting number of shares that will be earned. The cumulative effect on current and prior periods of a change in the estimated number of performance share units expected to be earned for these awards is recognized as compensation cost in earnings in the period of the change. For performance share units with a market-based relative TSR goal, stock-based compensation expense is recognized based on the estimated fair value of the award regardless of the actual number of shares earned. For further details regarding stock-based compensation, see Note 17. Fair Value Measurements The Company determines fair value measurements used in its consolidated financial statements based upon the exit price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants exclusive of any transaction costs, as determined by either the principal market or the most advantageous market. Inputs used in the valuation techniques to derive fair values are classified based on a three-level hierarchy. The basis for fair value measurements for each level within the hierarchy is described below with Level 1 having the highest priority and Level 3 having the lowest. Level 1: Quoted prices in active markets for identical assets or liabilities. Level 2: Quoted prices for similar assets or liabilities in active markets; quoted prices for identical or similar instruments in markets that are not active; and model-derived valuations in which all significant inputs are observable in active markets. Level 3: Valuations derived from valuation techniques in which one or more significant inputs are unobservable. Foreign Currency The Company predominately uses the U.S. dollar as its functional currency. The functional currency of the Company's foreign operating subsidiaries generally is the applicable local currency. Assets and liabilities denominated in non-U.S. dollars are translated into U.S. dollars at exchange rates as of the end of the reporting period. Income and expense items are translated at the average monthly exchange rates during the year. Resulting translation adjustments are recorded as a component of accumulated other comprehensive loss within stockholders' equity. Gains and losses from foreign currency transactions, which are denominated in a currency other than the functional currency, are included within other operating expense (income), net in the consolidated statements of operations. Foreign currency transaction gains and losses have historically not been material. The Company may be exposed to market risk for changes in foreign exchange rates primarily under certain intercompany receivables and payables. From time to time, the Company uses foreign exchange forward contracts to mitigate the exposure of the eventual net cash inflows or outflows resulting from these intercompany transactions. The Company's foreign exchange exposure is not material to the Company's consolidated financial condition. The Company does not hedge its net investment in non-U.S. subsidiaries because it views those investments as long-term in nature. Cash and Cash Equivalents Cash and cash equivalents include all highly-liquid investments with original maturities, at the time acquired by the Company, of three months or less. Concentration of Credit Risk Financial instruments that potentially subject the Company to concentrations of credit risk are principally cash, cash equivalents, short-term investments, accounts receivable and derivative financial instruments. The Company's policy is to place its cash, cash equivalents and short-term investments in highly-rated financial instruments and institutions. Concentration of credit risk with respect to accounts receivable is mitigated by the diversity of the Company's payers and their dispersion across many different geographic regions, and is limited to certain payers who are large buyers of the Company's services. To reduce risk, the Company routinely assesses the financial strength of these payers and, consequently, believes that its accounts receivable credit risk exposure, with respect to these payers, is limited. While the Company has receivables due from federal and state governmental agencies, the Company does not believe that such receivables represent a credit risk since the related healthcare programs are funded by federal and state governments, and payment is primarily dependent on submitting appropriate documentation timely. As of December 31, 2020 and 2019, receivables due from government payers under the Medicare and Medicaid programs represented approximately 6% and 11%, respectively, of the Company's consolidated net accounts receivable. The portion of the Company's accounts receivable due from patients comprises the largest portion of credit risk. As of December 31, 2020 and 2019, receivables due from patients represented approximately 11% and 20%, respectively, of the Company's consolidated net accounts receivable. The Company applies assumptions and judgments including historical collection experience (including the period the receivables have been outstanding) for assessing collectability and determining net revenues and accounts receivable from patients. Accounts Receivable and Allowance for Credit Losses Accounts receivable are reported net of allowances for credit losses. When estimating its allowance for credit losses, the Company pools its trade receivables based on the following customer types: healthcare insurers, government payers, client payers and patients, which are described in Note 3. The Company principally estimates the allowance for credit losses by pool based on historical collection experience, the current credit worthiness of the customers, current economic conditions, expectations of future economic conditions and the period that the receivables have been outstanding. To the extent that any individual payers are identified that have deteriorated in credit quality, the Company removes the customers from their respective pools and establishes allowances based on the individual risk characteristics of such customers. Inventories Inventories, which consist principally of finished goods testing supplies and reagents, are valued at the lower of cost (first in, first out method) or net realizable value. Property, Plant and Equipment Property, plant and equipment is recorded at cost. Major renewals and improvements are capitalized, while maintenance and repairs are expensed as incurred. Costs incurred for computer software developed or obtained for internal use are capitalized for application development activities and expensed as incurred for preliminary project activities and post-implementation activities. Capitalized costs include external direct costs of materials and services consumed in developing or obtaining internal-use software, payroll and payroll-related costs for employees who are directly associated with the internal-use software project, and interest costs incurred, when material, while developing internal-use software. Capitalization of such costs ceases when the project is substantially complete and ready for its intended purpose. Costs for maintenance and training are expensed as incurred. The Company capitalizes interest on borrowings during the active construction period of major capital projects. Capitalized interest is added to the cost of the underlying assets and is amortized over the expected useful lives of the assets. Depreciation and amortization are provided on the straight-line method over expected useful asset lives as of December 31, 2020 as follows: •buildings and improvements, ranging up to thirty-one and a half years; •laboratory equipment and furniture and fixtures, ranging from five to twelve years; •leasehold improvements, the lesser of the useful life of the improvement or the remaining life of the building or lease, as applicable; and •computer software developed or obtained for internal use, five to ten years. Goodwill Goodwill represents the excess of the fair value of the acquiree (including the fair value of non-controlling interests) over the recognized bases of the net identifiable assets acquired and includes the future economic benefits from other assets that could not be individually identified and separately recognized. Goodwill is not amortized, but instead is periodically reviewed for impairment and an impairment charge is recorded in the periods in which the recorded carrying value of goodwill exceeds its fair value. On a quarterly basis, the Company performs a review of its business to determine if events or changes in circumstances have occurred which could have a material adverse effect on the fair value of the Company and its goodwill. If such events or changes in circumstances were deemed to have occurred, the Company would perform an impairment test of goodwill as of the end of the quarter and record any noted impairment loss. The goodwill test is performed at least annually, or more frequently if events or changes in circumstances indicate that the asset might be impaired. The annual impairment test includes an option to perform a qualitative assessment of whether it is more likely than not that a reporting unit's fair value is less than its carrying value; the qualitative test may be performed prior to, or as an alternative to, performing a quantitative goodwill impairment test. If, after assessing the totality of events or circumstances, the Company determines that it is more likely than not that the fair value of a reporting unit is less than its carrying value, then the Company is required to perform the quantitative goodwill impairment test. Otherwise, no further analysis is required. Additionally, the Company's policy is to update the fair value calculation of its reporting units and perform the quantitative goodwill impairment test on a periodic basis. The quantitative impairment test involves the comparison of the fair value of the reporting unit to its carrying value. The Company calculates the fair value of each reporting unit using either (i) a discounted cash flows analysis that converts future cash flow amounts into a single discounted present value amount or (ii) a market approach. The Company assesses the valuation methodology based upon the relevance and availability of the data at the time that the valuation is performed. The Company compares the estimate of fair value for the reporting unit to the carrying value of the reporting unit. If the carrying value is greater than the estimate of fair value, an impairment loss will be recognized in the amount of the excess. The Company performs its annual impairment test during the fourth quarter of the fiscal year. For the year ended December 31, 2020, in accordance with its policy to perform the quantitative test on a periodic basis, the Company updated the fair value calculation of its reporting units, performed the quantitative impairment test and concluded that goodwill was not impaired. For the year ended December 31, 2019, the Company performed a qualitative impairment test and, based on the totality of information available for the reporting units, the Company concluded that it was more-likely-than-not that the estimated fair values of the reporting units were greater than the carrying values of the reporting units and, as such, no further analysis was required. Intangible Assets Intangible assets are recognized at fair value, as an asset apart from goodwill if the asset (i) arises from contractual or other legal rights, or (ii) is separable. Intangible assets, principally representing the cost of customer-related intangibles, non-competition agreements and technology acquired, are capitalized and amortized on the straight-line method over their expected useful lives, which generally range from five to twenty years. Intangible assets with indefinite useful lives, consisting principally of acquired tradenames, are not amortized, but instead are periodically reviewed for impairment. The Company reviews indefinite-lived intangible assets periodically for impairment and an impairment charge is recorded in the periods in which the recorded carrying value of an indefinite-lived intangible is more than its estimated fair value. The indefinite-lived intangible asset impairment test is performed at least annually, or more frequently in the case of other events that indicate a potential impairment. Based upon the Company’s most recent annual impairment tests completed during the fourth quarters of the years ended December 31, 2020 and 2019, the Company concluded that indefinite-lived intangible assets were not impaired. The Company reviews the recoverability of its long-lived assets (including amortizable intangible assets), other than goodwill and indefinite-lived intangible assets, when events or changes in circumstances occur that indicate that the carrying value of the asset may not be recoverable. Evaluation of possible impairment is based on the Company's ability to recover the asset from the expected future pre-tax cash flows (undiscounted and without interest charges) of the related operations. If these cash flows are less than the carrying amount of such asset, an impairment loss is recognized for the difference between the estimated fair value and carrying amount of the asset. Investments The Company's investments (except for those accounted for under the equity method of accounting), are included in other assets in the consolidated balance sheet and include: •Equity investments with readily determinable fair values which are comprised of participant-directed investments of deferred employee compensation and related Company matching contributions held in trusts pursuant to the Company's supplemental deferred compensation plans (see Note 17). These investments are measured at fair value with both realized and unrealized gains and losses recorded in current earnings within other income (expense), net in the consolidated statements of operations. For the years ended December 31, 2020, 2019 and 2018, gains and (losses) from these equity securities totaled $8 million, $10 million, and $(2) million, respectively. The carrying value of these investments were $67 million and $59 million at December 31, 2020 and 2019, respectively. •Equity investments that do not have readily determinable fair values, which consist of investments in preferred and common shares of privately held companies. These investments are measured at cost minus impairment, if any, plus or minus changes resulting from observable price changes. The Company regularly evaluates these equity investments to determine if there are any indicators that the investment is impaired; no impairment charges were recognized related to these investments for the years ended December 31, 2020, 2019, and 2018. The carrying value of these investments was $25 million at both December 31, 2020 and 2019. •Available-for-sale debt securities of privately-held companies. These investments are measured at fair value with unrealized gains and losses presented in other comprehensive income (loss). The carrying amount of these investments was $12 million at both December 31, 2020 and 2019. Derivative Financial Instruments The Company uses derivative financial instruments to manage its exposure to market risks for changes in interest rates and, from time to time, foreign currencies. This strategy includes the use of interest rate swap agreements, forward-starting interest rate swap agreements, interest rate lock agreements and foreign currency forward contracts to manage its exposure to movements in interest and currency rates. The Company has established policies and procedures for risk assessment and the approval, reporting and monitoring of derivative financial instrument activities. These policies prohibit holding or issuing derivative financial instruments for speculative purposes. The Company does not enter into derivative financial instruments that contain credit risk-related contingent features or requirements to post collateral. Interest Rate Risk The Company is exposed to interest rate risk on its cash and cash equivalents and its debt obligations. Interest income earned on cash and cash equivalents may fluctuate as interest rates change; however, due to their relatively short maturities, the Company does not hedge these assets or their investment cash flows and the impact of interest rate risk is not material. The Company's debt obligations consist of fixed-rate and variable-rate debt instruments. The Company's primary objective is to achieve the lowest overall cost of funding while managing the variability in cash outflows within an acceptable range. In order to achieve this objective, the Company has historically entered into interest rate swap agreements. Interest rate swap agreements involve the periodic exchange of payments without the exchange of underlying principal or notional amounts. Net settlements between the counterparties are recognized as an adjustment to interest expense, net. The Company accounts for these derivatives as either an asset or liability measured at its fair value. The fair value is based upon model-derived valuations in which all significant inputs are observable in active markets including certain financial information and certain assumptions regarding past, present and future market conditions. For a derivative instrument that has been formally designated as a fair value hedge, fair value gains or losses on the derivative instrument along with offsetting fair value gains or losses on the hedged item that are attributable to the risk being hedged are reported in other income (expense), net in the consolidated statements of operations. For derivatives that have been formally designated as a cash flow hedge, the change in the fair value of the derivatives is recorded in accumulated other comprehensive loss. Upon maturity or early termination of an effective interest rate swap agreement designated as a cash flow hedge, unrealized gains or losses are deferred in stockholders' equity, as a component of accumulated other comprehensive loss, and are amortized as an adjustment to interest expense over the period during which the hedged forecasted transaction affects earnings, which is when the Company recognizes interest expense on the hedged cash flows. At inception and quarterly thereafter, the Company formally assesses whether the derivatives that are used in hedging transactions are highly effective in offsetting changes in the fair value or cash flows of the hedged item. After the initial quantitative assessment, this analysis is initially performed on a qualitative basis and, if it is determined that the hedging relationship was and continues to be highly effective, no further analysis is required. All components of each derivative financial instrument's gain or loss are included in the assessment of hedge effectiveness. If it is determined that a derivative ceases to be a highly effective hedge, the Company discontinues hedge accounting and any deferred gains or losses related to a discontinued cash flow hedge shall continue to be reported in accumulated other comprehensive loss, unless it is probable that the forecasted transaction will not occur. If it is probable that the forecasted transaction will not occur by the originally specified time period, the Company discontinues hedge accounting and any deferred gains or losses reported in accumulated other comprehensive loss are classified into earnings immediately. Comprehensive Income (Loss) Comprehensive income (loss) encompasses all changes in stockholders' equity (except those arising from transactions with stockholders) and includes: •Foreign currency translation adjustments; •Net changes in available-for-sale debt securities, which represent unrealized holding gains (losses), net of tax, on available-for-sale debt securities; and •Net deferred gains (losses) on cash flow hedges, which represent deferred gains (losses), net of tax, on interest rate-related derivative financial instruments designated as cash flow hedges, net of amounts reclassified to interest expense (see Notes 15 and 16). New Accounting Standards Adoption of New Accounting Standards On January 1, 2020, the Company adopted a new accounting standard issued by the Financial Accounting Standards Board ("FASB") which aligns the requirements for deferring implementation costs incurred in a cloud computing arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The adoption of this standard, which the Company elected to do on a prospective basis, did not have a material impact on the Company's consolidated results of operations, financial position or cash flows. On January 1, 2020, the Company adopted a new accounting standard issued by the FASB that changes the impairment model for most financial instruments, including trade receivables, from an incurred loss method to a new forward looking approach, based on expected losses. The estimate of expected credit losses requires entities to incorporate considerations of historical information, current information and reasonable and supportable forecasts. The adoption of this new standard, which was done using a modified retrospective transition approach, did not have a material impact on the Company's consolidated results of operations, financial position or cash flows. See "Accounts Receivable and Allowance for Credit Losses" in this footnote for further details on the Company's allowance for credit losses policy. On January 1, 2019, the Company adopted a new accounting standard issued by the FASB on accounting for leases using the modified retrospective method. This new accounting standard requires a lessee to recognize on its balance sheet an asset and liability for most leases. The Company elected the optional transition method that allowed for a cumulative-effect adjustment to the opening balance of retained earnings recorded on January 1, 2019 and did not restate previously reported results in the comparative periods. The Company also elected the package of practical expedients, which among other things, allowed it to carry forward its historical lease classification. As a result of adoption of the new standard, the Company recorded operating lease assets and lease liabilities of approximately $500 million and $550 million, respectively as of January 1, 2019. The operating lease liability was determined based on the present value of the remaining minimum rental payments and the operating lease asset was determined based on the value of the lease liability, adjusted for the deferred rent balances of approximately $50 million, which were previously included in accounts payable and accrued expenses as well as other liabilities in the consolidated balance sheet. Accounting for the Company's finance leases remained substantially unchanged. The adoption of the new standard did not materially impact the Company's consolidated results of operations or cash flows. In addition, the adoption of this new accounting standard resulted in increased qualitative and quantitative disclosures regarding the amount, timing, and uncertainty of cash flows arising from leases. For further details, see Note 14. New Accounting Standards To Be Adopted In March 2020, the FASB issued a new accounting standard which provides temporary optional guidance to ease the potential burden in accounting for reference rate reform due to the risk of cessation of the London Interbank Offered Rate ("LIBOR"). The amendments apply only to contracts, hedging relationships, and other transactions that reference LIBOR or another reference rate expected to be discontinued because of reference rate reform. The pronouncement is effective immediately and can be applied through December 31, 2022. The adoption of this standard is not expected to have a material impact on the Company’s consolidated results of operations, financial position or cash flows.

The consolidated financial statements include the accounts of all entities controlled by the Company through its direct or indirect ownership of a majority voting interest. Additionally, the consolidated financial statements include the accounts of variable interest entities (“VIEs”) in which the Company has a variable interest and for which the Company is the “primary beneficiary” as it has both: (1) the power to direct the activities of the VIE that most significantly impact the VIE’s economic performance and (2) the obligation to absorb losses of the VIE that potentially could be significant to the VIE or the right to receive benefits from the VIE that potentially could be significant to the VIE. All significant intercompany accounts and transactions are eliminated in consolidation.

Investments in entities which the Company does not control, but in which it has a substantial ownership interest (generally between 20% and 49%) and can exercise significant influence, are accounted for using the equity method of accounting. These investments are classified as investments in equity method investees in the consolidated balance sheet. The Company records its pro rata share of the earnings, adjusted for accretion of basis difference, of these investments in equity in earnings of equity method investees, net of taxes in the consolidated statements of operations. The Company reviews its investments in equity method investees for impairment whenever events or changes in circumstances indicate that the carrying amounts may not be recoverable.

The provision for income taxes represents income taxes paid or payable for the current year plus the change in deferred taxes during the year. Current and deferred income taxes are measured based on the tax laws that are enacted as of the balance sheet date of the relevant reporting period. Deferred tax assets and liabilities are recognized for the expected future tax consequences of differences between the carrying amounts of assets and liabilities and their respective tax bases using tax rates in effect for the year in which the differences are expected to reverse. A valuation allowance is provided when it is more likely than not that some portion or all of the deferred tax assets will not be realized. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period when the change is enacted. Tax benefits from uncertain tax positions are recognized only if the tax position is more likely than not to be sustained upon examination by taxing authorities based on the technical merits of the position.

The Company's unvested restricted stock units that contain non-forfeitable rights to dividends are participating securities and, therefore, are included in the earnings allocation in computing earnings per share using the two-class method. Basic earnings per common share is calculated by dividing net income attributable to Quest Diagnostics, adjusted for earnings allocated to participating securities, by the weighted average number of common shares outstanding. Diluted earnings per common share is calculated by dividing net income attributable to Quest Diagnostics, adjusted for earnings allocated to participating securities, by the weighted average number of common shares outstanding after giving effect to all potentially dilutive common shares outstanding during the period. Potentially dilutive common shares include the dilutive effect of outstanding stock options and performance share units granted under the Company's Amended and Restated Employee Long-Term Incentive Plan (“ELTIP”) and its Amended and Restated Non-Employee Director Long-Term Incentive Plan (“DLTIP”). Earnings allocable to participating securities include the portion of dividends declared as well as the portion of undistributed earnings during the period allocable to participating securities.

The Company measures stock-based compensation for equity awards at fair value on the date of grant and records stock-based compensation as a charge to earnings net of the estimated impact of forfeited awards. As such, the Company recognizes stock-based compensation cost only for those stock-based awards that are estimated to ultimately vest over their requisite service period, based on the vesting provisions of the individual grants. The cumulative effect on current and prior periods of a change in the estimated forfeiture rate is recognized as compensation cost in earnings in the period of the change. The terms of the Company's performance share units allow the recipients of such awards to earn a variable number of shares based on the achievement of the performance goals, which are based on the financial performance of the Company and the total shareholder return of the Company relative to an index of peer companies ("relative TSR"), specified in the awards. For performance share units with a goal based on the financial performance of the Company, stock-based compensation expense is recognized based on management's best estimates of the achievement of the performance goals specified in such awards and the resulting number of shares that will be earned. The cumulative effect on current and prior periods of a change in the estimated number of performance share units expected to be earned for these awards is recognized as compensation cost in earnings in the period of the change. For performance share units with a market-based relative TSR goal, stock-based compensation expense is recognized based on the estimated fair value of the award regardless of the actual number of shares earned. For further details regarding stock-based compensation, see Note 17.

The Company predominately uses the U.S. dollar as its functional currency. The functional currency of the Company's foreign operating subsidiaries generally is the applicable local currency. Assets and liabilities denominated in non-U.S. dollars are translated into U.S. dollars at exchange rates as of the end of the reporting period. Income and expense items are translated at the average monthly exchange rates during the year. Resulting translation adjustments are recorded as a component of accumulated other comprehensive loss within stockholders' equity. Gains and losses from foreign currency transactions, which are denominated in a currency other than the functional currency, are included within other operating expense (income), net in the consolidated statements of operations. Foreign currency transaction gains and losses have historically not been material. The Company may be exposed to market risk for changes in foreign exchange rates primarily under certain intercompany receivables and payables. From time to time, the Company uses foreign exchange forward contracts to mitigate the exposure of the eventual net cash inflows or outflows resulting from these intercompany transactions. The Company's foreign exchange exposure is not material to the Company's consolidated financial condition. The Company does not hedge its net investment in non-U.S. subsidiaries because it views those investments as long-term in nature.

Financial instruments that potentially subject the Company to concentrations of credit risk are principally cash, cash equivalents, short-term investments, accounts receivable and derivative financial instruments. The Company's policy is to place its cash, cash equivalents and short-term investments in highly-rated financial instruments and institutions. Concentration of credit risk with respect to accounts receivable is mitigated by the diversity of the Company's payers and their dispersion across many different geographic regions, and is limited to certain payers who are large buyers of the Company's services. To reduce risk, the Company routinely assesses the financial strength of these payers and, consequently, believes that its accounts receivable credit risk exposure, with respect to these payers, is limited. While the Company has receivables due from federal and state governmental agencies, the Company does not believe that such receivables represent a credit risk since the related healthcare programs are funded by federal and state governments, and payment is primarily dependent on submitting appropriate documentation timely. As of December 31, 2020 and 2019, receivables due from government payers under the Medicare and Medicaid programs represented approximately 6% and 11%, respectively, of the Company's consolidated net accounts receivable. The portion of the Company's accounts receivable due from patients comprises the largest portion of credit risk. As of December 31, 2020 and 2019, receivables due from patients represented approximately 11% and 20%, respectively, of the Company's consolidated net accounts receivable. The Company applies assumptions and judgments including historical collection experience (including the period the receivables have been outstanding) for assessing collectability and determining net revenues and accounts receivable from patients.

When estimating its allowance for credit losses, the Company pools its trade receivables based on the following customer types: healthcare insurers, government payers, client payers and patients, which are described in Note 3. The Company principally estimates the allowance for credit losses by pool based on historical collection experience, the current credit worthiness of the customers, current economic conditions, expectations of future economic conditions and the period that the receivables have been outstanding. To the extent that any individual payers are identified that have deteriorated in credit quality, the Company removes the customers from their respective pools and establishes allowances based on the individual risk characteristics of such customers.

Property, plant and equipment is recorded at cost. Major renewals and improvements are capitalized, while maintenance and repairs are expensed as incurred. Costs incurred for computer software developed or obtained for internal use are capitalized for application development activities and expensed as incurred for preliminary project activities and post-implementation activities. Capitalized costs include external direct costs of materials and services consumed in developing or obtaining internal-use software, payroll and payroll-related costs for employees who are directly associated with the internal-use software project, and interest costs incurred, when material, while developing internal-use software. Capitalization of such costs ceases when the project is substantially complete and ready for its intended purpose. Costs for maintenance and training are expensed as incurred. The Company capitalizes interest on borrowings during the active construction period of major capital projects. Capitalized interest is added to the cost of the underlying assets and is amortized over the expected useful lives of the assets. Depreciation and amortization are provided on the straight-line method over expected useful asset lives as of December 31, 2020 as follows:

Goodwill represents the excess of the fair value of the acquiree (including the fair value of non-controlling interests) over the recognized bases of the net identifiable assets acquired and includes the future economic benefits from other assets that could not be individually identified and separately recognized. Goodwill is not amortized, but instead is periodically reviewed for impairment and an impairment charge is recorded in the periods in which the recorded carrying value of goodwill exceeds its fair value.

The goodwill test is performed at least annually, or more frequently if events or changes in circumstances indicate that the asset might be impaired. The annual impairment test includes an option to perform a qualitative assessment of whether it is more likely than not that a reporting unit's fair value is less than its carrying value; the qualitative test may be performed prior to, or as an alternative to, performing a quantitative goodwill impairment test. If, after assessing the totality of events or circumstances, the Company determines that it is more likely than not that the fair value of a reporting unit is less than its carrying value, then the Company is required to perform the quantitative goodwill impairment test. Otherwise, no further analysis is required. Additionally, the Company's policy is to update the fair value calculation of its reporting units and perform the quantitative goodwill impairment test on a periodic basis.

The quantitative impairment test involves the comparison of the fair value of the reporting unit to its carrying value. The Company calculates the fair value of each reporting unit using either (i) a discounted cash flows analysis that converts future cash flow amounts into a single discounted present value amount or (ii) a market approach. The Company assesses the valuation methodology based upon the relevance and availability of the data at the time that the valuation is performed. The Company compares the estimate of fair value for the reporting unit to the carrying value of the reporting unit. If the carrying value is greater than the estimate of fair value, an impairment loss will be recognized in the amount of the excess.

The Company performs its annual impairment test during the fourth quarter of the fiscal year. For the year ended December 31, 2020, in accordance with its policy to perform the quantitative test on a periodic basis, the Company updated the fair value calculation of its reporting units, performed the quantitative impairment test and concluded that goodwill was not impaired. For the year ended December 31, 2019, the Company performed a qualitative impairment test and, based on the totality of information available for the reporting units, the Company concluded that it was more-likely-than-not that the estimated fair values of the reporting units were greater than the carrying values of the reporting units and, as such, no further analysis was required.

Intangible assets are recognized at fair value, as an asset apart from goodwill if the asset (i) arises from contractual or other legal rights, or (ii) is separable. Intangible assets, principally representing the cost of customer-related intangibles, non-competition agreements and technology acquired, are capitalized and amortized on the straight-line method over their expected useful lives, which generally range from five to twenty years. Intangible assets with indefinite useful lives, consisting principally of acquired tradenames, are not amortized, but instead are periodically reviewed for impairment.

The Company reviews the recoverability of its long-lived assets (including amortizable intangible assets), other than goodwill and indefinite-lived intangible assets, when events or changes in circumstances occur that indicate that the carrying value of the asset may not be recoverable. Evaluation of possible impairment is based on the Company's ability to recover the asset from the expected future pre-tax cash flows (undiscounted and without interest charges) of the related operations. If these cash flows are less than the carrying amount of such asset, an impairment loss is recognized for the difference between the estimated fair value and carrying amount of the asset.

•Equity investments with readily determinable fair values which are comprised of participant-directed investments of deferred employee compensation and related Company matching contributions held in trusts pursuant to the Company's supplemental deferred compensation plans (see Note 17). These investments are measured at fair value with both realized and unrealized gains and losses recorded in current earnings within other income (expense), net in the consolidated statements of operations. For the years ended December 31, 2020, 2019 and 2018, gains and (losses) from these equity securities totaled $8 million, $10 million, and $(2) million, respectively. The carrying value of these investments were $67 million and $59 million at December 31, 2020 and 2019, respectively.

•Equity investments that do not have readily determinable fair values, which consist of investments in preferred and common shares of privately held companies. These investments are measured at cost minus impairment, if any, plus or minus changes resulting from observable price changes. The Company regularly evaluates these equity investments to determine if there are any indicators that the investment is impaired; no impairment charges were recognized related to these investments for the years ended December 31, 2020, 2019, and 2018. The carrying value of these investments was $25 million at both December 31, 2020 and 2019.

The Company uses derivative financial instruments to manage its exposure to market risks for changes in interest rates and, from time to time, foreign currencies. This strategy includes the use of interest rate swap agreements, forward-starting interest rate swap agreements, interest rate lock agreements and foreign currency forward contracts to manage its exposure to movements in interest and currency rates. The Company has established policies and procedures for risk assessment and the approval, reporting and monitoring of derivative financial instrument activities. These policies prohibit holding or issuing derivative financial instruments for speculative purposes. The Company does not enter into derivative financial instruments that contain credit risk-related contingent features or requirements to post collateral.

The Company is exposed to interest rate risk on its cash and cash equivalents and its debt obligations. Interest income earned on cash and cash equivalents may fluctuate as interest rates change; however, due to their relatively short maturities, the Company does not hedge these assets or their investment cash flows and the impact of interest rate risk is not material. The Company's debt obligations consist of fixed-rate and variable-rate debt instruments. The Company's primary objective is to achieve the lowest overall cost of funding while managing the variability in cash outflows within an acceptable range. In order to achieve this objective, the Company has historically entered into interest rate swap agreements. Interest rate swap agreements involve the periodic exchange of payments without the exchange of underlying principal or notional amounts. Net settlements between the counterparties are recognized as an adjustment to interest expense, net.

The Company accounts for these derivatives as either an asset or liability measured at its fair value. The fair value is based upon model-derived valuations in which all significant inputs are observable in active markets including certain financial information and certain assumptions regarding past, present and future market conditions. For a derivative instrument that has been formally designated as a fair value hedge, fair value gains or losses on the derivative instrument along with offsetting fair value gains or losses on the hedged item that are attributable to the risk being hedged are reported in other income (expense), net in the consolidated statements of operations. For derivatives that have been formally designated as a cash flow hedge, the change in the fair value of the derivatives is recorded in accumulated other comprehensive loss. Upon maturity or early termination of an effective interest rate swap agreement designated as a cash flow hedge, unrealized gains or losses are deferred in stockholders' equity, as a component of accumulated other comprehensive loss, and are amortized as an adjustment to interest expense over the period during which the hedged forecasted transaction affects earnings, which is when the Company recognizes interest expense on the hedged cash flows. At inception and quarterly thereafter, the Company formally assesses whether the derivatives that are used in hedging transactions are highly effective in offsetting changes in the fair value or cash flows of the hedged item. After the initial quantitative assessment, this analysis is initially performed on a qualitative basis and, if it is determined that the hedging relationship was and continues to be highly effective, no further analysis is required. All components of each derivative financial instrument's gain or loss are included in the assessment of hedge effectiveness. If it is determined that a derivative ceases to be a highly effective hedge, the Company discontinues hedge accounting and any deferred gains or losses related to a discontinued cash flow hedge shall continue to be reported in accumulated other comprehensive loss, unless it is probable that the forecasted transaction will not occur. If it is probable that the forecasted transaction will not occur by the originally specified time period, the Company discontinues hedge accounting and any deferred gains or losses reported in accumulated other comprehensive loss are classified into earnings immediately.

On January 1, 2020, the Company adopted a new accounting standard issued by the Financial Accounting Standards Board ("FASB") which aligns the requirements for deferring implementation costs incurred in a cloud computing arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The adoption of this standard, which the Company elected to do on a prospective basis, did not have a material impact on the Company's consolidated results of operations, financial position or cash flows.

looking approach, based on expected losses. The estimate of expected credit losses requires entities to incorporate considerations of historical information, current information and reasonable and supportable forecasts. The adoption of this new standard, which was done using a modified retrospective transition approach, did not have a material impact on the Company's consolidated results of operations, financial position or cash flows. See "Accounts Receivable and Allowance for Credit Losses" in this footnote for further details on the Company's allowance for credit losses policy.

On January 1, 2019, the Company adopted a new accounting standard issued by the FASB on accounting for leases using the modified retrospective method. This new accounting standard requires a lessee to recognize on its balance sheet an asset and liability for most leases. The Company elected the optional transition method that allowed for a cumulative-effect adjustment to the opening balance of retained earnings recorded on January 1, 2019 and did not restate previously reported results in the comparative periods. The Company also elected the package of practical expedients, which among other things, allowed it to carry forward its historical lease classification.

As a result of adoption of the new standard, the Company recorded operating lease assets and lease liabilities of approximately $500 million and $550 million, respectively as of January 1, 2019. The operating lease liability was determined based on the present value of the remaining minimum rental payments and the operating lease asset was determined based on the value of the lease liability, adjusted for the deferred rent balances of approximately $50 million, which were previously included in accounts payable and accrued expenses as well as other liabilities in the consolidated balance sheet. Accounting for the Company's finance leases remained substantially unchanged. The adoption of the new standard did not materially impact the Company's consolidated results of operations or cash flows.