Summary of Significant Accounting Policies | NOTE 2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation The consolidated financial statements and accompanying notes are prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) and the rules and regulations of the Securities and Exchange Commission (“SEC”). The consolidated financial statements of Oak Street Health include the financial statements of all wholly-owned subsidiaries and majority-owned or controlled entities. For those consolidated subsidiaries where our ownership is less than 100%, the portion of the net income or loss allocable to the noncontrolling interests is reported as “Net loss (gain) attributable to noncontrolling interests” in the consolidated statements of operations. The Company records a non-controlling interest for the portion attributable to its minority partners for all of its joint ventures. Intercompany balances and transactions have been eliminated in consolidation. Business combinations accounted for as purchases have been included from their respective dates of acquisition. Upon completion of the IPO, our sole material asset is our interest in OSH LLC and its affiliates. In accordance with the master structuring agreement dated August 10, 2020, by and among Oak Street Health, Inc. and the other signatories party thereto (the “Master Structuring Agreement”), we have all management powers over the business and affairs of OSH LLC and to conduct, direct and exercise full control over the activities of OSH LLC. Due to our power to control the activities most directly affecting the results of OSH LLC, we are considered the primary beneficiary of the variable interest entity (“VIE”). Accordingly, following the effective date of the IPO, we consolidate the financial results of OSH LLC and its affiliates and the financial statements for the periods prior to the IPO have been adjusted to combine the previously separate entities for presentation purposes. Variable Interest Entities The Company evaluates its ownership, contractual and other interests in entities to determine if it has any variable interest in a VIEs. These evaluations are complex, involve judgment, and the use of estimates and assumptions based on available historical information, among other factors. The Company considers itself to control an entity if it is the majority owner of or has voting control over such entity. The Company also assesses control through means other than voting rights (“variable interest entities” or “VIEs”) and determines which business entity is the primary beneficiary of the VIE. The Company consolidates VIEs when it is determined that the Company is the primary beneficiary of the VIE. Management performs ongoing reassessments of whether changes in the facts and circumstances regarding the Company’s involvement with a VIE will cause the consolidation conclusion to change. Changes in consolidation status are applied prospectively (see Note 15). In addition to the consolidated VIEs, Oak Street Health is the majority interest owner in three joint ventures: OSH-PCJ Joliet, LLC (50.1% ownership), OSH-RI, LLC (50.1% ownership), and OSH-ESC Joint Venture, LLC (51.0% ownership) which are consolidated in the Company’s financial statements. The following table illustrates the contributions and distributions made to and from the joint venture and Oak Street Health MSO, LLC for the periods then ended ($ in millions): For the twelve-months ended December 31, 2021 December 31, 2020 December 31, 2019 OSH-PCJ Joliet, LLC Contributions $ - $ - $ - Distributions 1.5 0.1 - OSH-RI, LLC Contributions 4.1 5.9 - Distributions - - - OSH-ESC Joint Venture, LLC Contributions 0.1 - 2.6 Distributions - - - Use of Estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. The Company bases its estimates on the information available at the time, its experiences and various other assumptions believed to be reasonable under the circumstances including estimates of the impact of COVID-19. The areas where significant estimates are used in the accompanying financial statements include revenue recognition, the liability for unpaid claims, projected cash flows in assessing the initial valuation of intangible assets in conjunction with business combinations and the valuation of stock options. Actual results could differ from those estimates. Cash, Cash Equivalents and Restricted Cash Cash and cash equivalents consist of currency on hand with banks and financial institutions and investments in money market funds. The Company considers all short-term, highly liquid investments with an original maturity of three months or less at the date of purchase to be cash equivalents. Restricted cash are funds held in Company bank accounts that are not available for operational use. The restricted cash balance consists of reserve accounts that are contractually required by payor contracts, and bank issued letters of credit. Marketable Debt Securities The Company’s investments in marketable debt securities are classified as available-for-sale and are carried at fair value, with the unrealized gains and losses reported as a component of accumulated other comprehensive income (loss) in total equity (deficit). The Company determines the appropriate classification of these investments at the time of purchase and reevaluates such designation at each balance sheet date. The Company classifies the available-for-sale investments as current assets under the caption marketable debt securities on the consolidated balance sheets as these investments generally consist of highly marketable securities that are identified to be available to meet near-term cash requirements and fund current operations. Realized gains and losses and declines in value related to credit losses are included as a component of other (expense) income, net in the consolidated statements of operations. The Company periodically evaluates its investments in marketable debt securities for impairment. When assessing short-term marketable security investments for declines in value, the Company considers such factors as, among other things, how significant the decline in value is as a percentage of the original cost, the Company’s ability and intent to retain the short-term marketable security investment for a period of time sufficient to allow for any anticipated recovery in fair value, market conditions in general and whether the decline in value is due to a credit loss. If any adjustment to fair value reflects a decline in the value of the marketable security that the Company considers to be for non-credit related factors, the Company reduces the marketable debt securities through a charge to the consolidated statement of operations. If a decline in value is determined to be related to a credit loss, we record an allowance not greater than the difference between the carrying amount and fair value of the investment. No such adjustments were necessary during the periods presented. Concentration of Credit Risk and Significant Customers Financial instruments that potentially subject the Company to concentration of credit risk consist of accounts receivable. The Company’s concentration of credit risk is limited by the diversity, geography and number of patients and payers. As of December 31, 2021 and 20 20 , the Company had customers that individually represented 10% or more of the Company’s capitated accounts receivable and other receivable s . The capitated accounts receivables by payor source consisted of the following as of: For the twelve-months ended December 31, 2021 December 31, 2020 Aetna 10 % 12 % Anthem 8 % 10 % Humana 19 % 26 % Medicare 17 % 0 % Wellcare/Meridian 19 % 21 % United Healthcare 12 % 14 % Other 15 % 17 % The other receivables by payor source consisted of the following as of: For the twelve-months ended December 31, 2021 December 31, 2020 Medicare 37 % 52 % Humana 13 % 8 % Other 50 % 40 % Property and Equipment The Company records property and equipment (“PPE”) at cost and depreciates them using the straight-line method at rates designed to distribute the cost of PPE over estimated service lives ranging from three to fifteen years. Routine maintenance and repairs are expensed as incurred. Expenditures that increase values, change capacities or extend useful lives are capitalized. When assets are sold or retired, the cost and related accumulated depreciation are removed from the accounts, with any resulting gain or loss recorded in corporate, general and administrative expenses in the consolidated statements of operations. Estimated useful lives of PPE are as follows: Leasehold improvements 15 years or term of lease Furniture and fixtures 8 years Computer equipment 3-5 years Internal use software 5 years Office equipment 5-8 years Internal Use Software The Company accounts for costs incurred to develop computer software for internal use in accordance with Accounting Standards Codification (“ASC”) 350-40, Internal-Use Software Impairment of Long-Lived Assets The Company reviews its long-lived assets for possible impairment in accordance with ASC 360, Property, Plant, and Equipment Investments in Securities The Company’s investments primarily include equity securities that are being accounted for by the equity method of accounting under which the Company’s share of net income or loss is recognized as income or loss in the Company’s statements of operations and added or deducted to the investment account. Distributions or dividends received from the investments are treated as a reduction of the investment account. The Company consistently follows the practice of recognizing the net income (loss) from equity method investments based on the most recent reliable data. The carrying value of the Company’s investments in was $5.0 million and $0.0 million as of December 31, 2021 and 2020, respectively, which is recorded in other long-term assets on the consolidated balance sheets. The Company did not identify any observable price changes for the years ended December 31, 2021, 2020 and 2019. Convertible Debt The Company evaluates all conversion, repurchase and redemption features contained in a debt instrument to determine if there are any embedded features that require bifurcation as a derivative. In accounting for the issuance of the 0% Convertible Senior Notes due 2026 issued in March 2021 (the “Convertible Senior Notes”), the Company recorded a long-term debt liability equal to the proceeds received from issuance, including the embedded conversion feature, net of the debt issuance and offering costs on the Company’s consolidated balance sheets. The conversion feature is not required to be accounted for separately as an embedded derivative. The Company amortizes debt issuance and offering costs over the term of the Convertible Senior Notes as interest expense utilizing the effective interest method on the Company’s consolidated statements of operations. Capped Call Transactions In connection with the issuance of the Convertible Senior Notes, the Company entered into capped call transactions. The capped call transactions are expected generally to reduce the potential dilution to the holders of the Company’s common stock upon any conversion of the Convertible Senior Notes. The capped call transactions are purchased call options on the issuer’s stock that settle by reference to the Company’s stock with no forced cash payment. The terms of the capped call transactions allow the purchased call options to be classified as an equity instrument and will not be subsequently remeasured as long as the conditions for equity classification continue to be met. The Company recorded the cash used to purchase the capped call transactions as a reduction to additional paid-in capital within the Company’s consolidated statements of changes in redeemable investor units and stockholders’ equity/members’ (deficit). Leases The Company leases offices, operating facilities, vehicles and IT equipment, which are accounted for as operating leases. These leases have remaining lease terms of up to 30 years, inclusive of renewal or termination options that the Company is reasonably certain to exercise. The Company determines if an arrangement is a lease at inception and evaluates the lease classification (i.e., operating lease or financing lease) at that time. Lease arrangements with an initial term of 12 months or less are considered short-term leases and are not recorded on the balance sheet. The Company recognizes lease expense for these leases on a straight-line basis over the term of the lease. Operating leases are included in operating lease right-of-use assets , The Company uses its incremental borrowing rate on the commencement date for determining the present value of lease payments. The Company considers the likelihood of exercising options to extend or terminate the lease when determining the lease term. The Company has lease agreements with lease and non-lease components. The Company has elected the practical expedient to account for the lease and non-lease components as a single lease component for all leases. Fair Value of Financial Instruments Fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Our financial assets and liabilities that require recognition and fair value measurement under the accounting guidance generally include our marketable debt securities, contingent consideration, and convertible debt (see Note 7). Income Taxes Prior to the IPO and related restructuring transactions, the Company was a limited liability company. Accordingly, pursuant to its election under Section 701 of the Internal Revenue Code, each item of income, gain, loss, deduction or credit of the Company was ultimately reportable by its members in their individual tax returns, except in certain states and local jurisdictions where the Company was subject to income taxes. As such, the Company did not record a provision for federal income taxes or for taxes in states and local jurisdictions that did not assess taxes at the entity level. After the IPO and related restructuring transactions, the Company is a C Corporation and each item of income, gain, loss, deduction or credit of the Company is reportable by the Company. As such, the Company has recorded a provision for federal, state, and local income taxes at the entity level in continuing operations for all deferred taxes net of the valuation allowance and activity post IPO. We account for income taxes under the liability method; under this method, deferred tax assets and liabilities are determined based on differences between financial reporting and tax reporting bases of assets and liabilities and are measured using enacted tax rates and laws that are expected to be in effect when the differences are expected to reverse. Realization of deferred tax assets is dependent upon future earnings, the timing and amount of which are uncertain. A tax position is recognized as a benefit only if it is more likely than not that the tax position would be sustained in a tax examination, with a tax examination being presumed to occur. The amount recognized is the largest amount of tax benefit that is greater than 50% likely of being realized on examination. For tax positions not meeting the more-likely-than-not test, no tax benefit is recorded. The Company’s tax filings are generally subject to examination for a period of three years from the filing date. Management has not identified any material tax position taken that requires income tax reserves to be established. The Company does not expect the total amount of unrecognized tax benefits to significantly change in the next twelve months. The Company reduces its deferred tax assets by a valuation allowance if it is more likely than not that some portion or all of a deferred tax asset will not be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences are deductible. In making this determination, the Company considers all available positive and negative evidence affecting specific deferred tax assets, including past and anticipated future performance, the reversal of deferred tax liabilities, the length of carry-back and carry-forward periods and the implementation of tax planning strategies. Objective positive evidence is necessary to support a conclusion that a valuation allowance is not needed for all or a portion of deferred tax assets when significant negative evidence exists. Cumulative tax losses in recent years are the most compelling form of negative evidence considered by management in this determination. Management determined that based on all available evidence, a full valuation allowance was required for all U.S. state and local deferred tax assets due to losses incurred for the past several years. Segment Reporting The Company determined in accordance with ASC 280, Segment Reporting (“ASC 280”), that the Company operates under one operating segment, and therefore one reportable segment – Oak Street Health, Inc. The Company’s chief operating decision makers (“CODMs”) regularly review financial operating results on a consolidated basis for purposes of allocating resources and evaluating financial performance. Our CODM has been identified as, collectively, the Chief Executive Officer, President, Chief Financial Officer and Chief Operating Officer. Although the Company derives its revenues from several different geographic regions, the Company neither allocates resources based on the operating results from the individual regions nor manages each individual region as a separate business unit. The Company’s CODMs manage the operations on a consolidated basis to make decisions about overall corporate resource allocation and to assess overall corporate profitability based on consolidated revenues, net income and adjusted EBITDA. For the periods presented, all of the Company’s long-lived assets were located in the United States, and all revenues were earned in the United States. As such, we have identified a single operating segment and reportable segment. Business Combinations, Goodwill and Other Intangible Assets The Company accounts for business combinations using the acquisition method of accounting. That method requires that the purchase price, including the fair value of contingent consideration, of the acquisition be allocated to the assets acquired and liabilities assumed using the fair values determined by management as of the acquisition date. Goodwill represents the excess of consideration paid over the fair value of net assets acquired through business acquisitions The Company performs a qualitative goodwill impairment analysis annually on October 1st or more frequently if triggering events occur or other impairment indicators arise which might impair recoverability. Identified intangibles are recorded at their acquisition date fair value and are amortized on a straight-line basis over their useful lives. Intangible assets are reviewed for impairment in conjunction with long-lived assets. There were no intangible asset impairments recorded during the years ended December 31, 2021, 2020 and 2019. Acquisition related transaction costs, such as banking, legal, accounting, and other costs incurred in connection with an acquisition are expensed as incurred in corporate, general and administrative expenses in the consolidated statements of operations. Acquisition related consideration accounted for as compensation expense, such as retention bonuses, incurred in connection with an acquisition are included in corporate, general and administrative expenses in the consolidated statements of operations. See Note 5, Business Combinations, Goodwill and Other Intangibles, for additional information. Medical Claims Expense Medical claims expense and the liability for unpaid claims include estimates of the Company’s obligations for medical care services that have been rendered by third parties on behalf of insured consumers for which the Company is contractually obligated to pay (see Note 3 for further detail), but for which claims have either not yet been received, processed or paid. The Company develops estimates for medical care services incurred but not reported (“IBNR”), which includes estimates for claims that have not been received or fully processed, using a process that is consistently applied, centrally controlled and automated. This process includes utilizing actuarial models when a sufficient amount of medical claims history is available from the third-party healthcare service providers. The actuarial models consider factors such as time from date of service to claim processing, seasonal variances in medical care consumption, health care professional contract rate changes, medical care utilization and other medical cost trends, membership volume and demographics, the introduction of new technologies and benefit plan changes. In developing its unpaid claims liability estimates, the Company applies different estimation methods depending on which incurred claims are being estimated. We assess our estimates with an independent actuarial expert to ensure our estimates represent the best, most reasonable estimate given the data available to us at the time the estimates are made. Medical claims expense also includes supplemental external costs of providing medical care such as administrative health plan fees, fees to perform payor delegated activities and provider excess insurance costs. The Company purchases provider excess insurance to protect against significant, catastrophic claims expenses incurred on behalf of its patients. The total amount of provider excess insurance premium was $4.6 million, $3.6 million and $2.5 million, and total reimbursements were $4.7 million, $3.1 million and $1.0 million for the years ended December 31, 2021, 2020 and 2019, respectively. The provider excess insurance premiums less reimbursements are reported in medical claims expense in the consolidated statements of operations. Provider excess recoverables due are reported in other current assets in the consolidated balance sheets. As of December 31, 2021 and 2020, the Company’s provider excess insurance deductible was $0.3 million per member and covered up to a maximum of $5.0 million per member per calendar year. Cost of Care, Excluding Depreciation and Amortization Cost of care, excluding depreciation and amortization includes the costs we incur to operate our centers and care model, including care team and patient support employee-related costs, occupancy costs, patient transportation, medical supplies, insurance, fees paid to specialists and other operating costs. These costs exclude any expenses associated with sales and marketing activities incurred at the local level to support our patient growth strategies, and excludes any allocation of our corporate, general and administrative expenses. Care team employees include medical doctors, nurse practitioners, physician assistants, registered nurses, scribes, medical assistants and phlebotomists. Patient support employees include practice managers, welcome coordinators and patient relationship managers. Sales and Marketing Sales and marketing expenses consist of employee-related expenses, including salaries, commissions, stock-based compensation and employee benefits costs, for all of our employees engaged in marketing, sales, community outreach and sales support. These employee-related expenses capture all costs for both our field-based and corporate sales and marketing teams. Sales and marketing expenses also includes central and community-based advertising to generate greater awareness, engagement, and retention among our current and prospective patients as well as the infrastructure required to support all our marketing efforts. Corporate, General and Administrative Corporate, general and administrative expenses include employee-related expenses, including salaries and related costs and stock/ unit-based compensation for our executives, technology infrastructure, operations, clinical and quality support, finance, legal, human resources and development departments. In addition, general and administrative expenses include all corporate technology and occupancy costs. Transaction Costs The Company incurred costs related to private/public offerings and acquisitions. Total one-time costs expensed were $5.9 million, $1.1 million and $3.7 million for the years ended December 31, 2021, 2020 and 2019 Advertising Expenses Advertising and promotion costs are expensed as incurred and were $54.4 million, $29.3 million and $16.8 million, for the years ended December 31, 2021, 2020 and 2019, respectively, and are included in sales and marketing expenses in the consolidated statements of operations. Retirement Plan The Company maintains a profit sharing and retirement savings 401(k) plan (the “401(k) Plan”) for full-time employees. Participants may elect to contribute to the 401(k) Plan, through payroll deductions, subject to Internal Revenue Service limitations. At its discretion, the Company makes 4% matching and/or profit-sharing contributions to the 401(k) Plan. The Company recorded expense of $7.1 million, $4.7 million, and $3.1 million in salaries and employee benefits in the accompanying consolidated statements of operations for the years ended December 31, 2021, 2020 and 2019, respectively, for discretionary matching and profit-sharing contributions to the 401(k) Plan. Professional Liability The physicians employed by the Physician Groups (or PC entities) were insured for professional liability exposure on a claims-made basis with a master insurance policy issued by CNA. The master policy renews in August of each year and newly employed physicians and terminating physicians are added or deleted to the coverage by endorsement, with premiums prorated to the next year’s expiration date. The limits of the coverage are $1.0 million each claim and $3.0 million in aggregate. Additional insureds on the policy include the PC entities, the physician employees and OSH MSO. Stock/ Unit-Based Compensation Expense Following the IPO, we account for stock-based compensation awards approved by our Board of Directors, including stock options and restricted stock units (“RSUs”), based on their estimated grant date fair value in accordance with ASC 718, Compensation—Stock Compensation We recognize fair value of stock options at the grant date, which vest based on continued service at a rate of 25% each year, over the requisite service period, which is generally four years. Options generally expire ten years from the date of the grant. Prior to the IPO, the Company’s unit-based incentive plan rewarded employees with various types of awards, including but not limited to, profits interests on a service-based or performance-based schedule. These awards also contained market conditions. The Company had elected to account for forfeitures as they occur. The Company used a combination of the income and market approaches to estimate the fair value of each award as of the grant date. For performance-vesting units pre-IPO, the Company recognized unit-based compensation expense when it was probable that the performance condition would be achieved. The Company analyzed if a performance condition was probable for each reporting period through the settlement date for awards subject to performance vesting. For service-vesting units, the Company recognized unit-based compensation expense over the requisite service period for each separately vesting portion of the profits interest as if the award was, in-substance, multiple awards. Net Income (Loss) Per Share Prior to the IPO, the OSH LLC membership structure included pre-IPO units, some of which were investor units and profits interests (see further discussion in section, Initial Public Offering The Company analyzed the calculation of earnings per unit for periods prior to the IPO and determined that it resulted in values that would not be meaningful to the users of these consolidated financial statements. Therefore, earnings per share information has not been presented for the year ended December 31, 2019. The basic and diluted earnings per share for the year ended December 31, 2020 is applicable only for the period from August 10, 2020 to December 31, 2020, which is the period following the IPO and related restructuring transactions (as described in Note 1) and presents the period that the Company had outstanding common stock. Basic net loss per share attributable to common shareholders is calculated by dividing the net loss by the weighted-average number of common shares outstanding during the period, without consideration for common share equivalents. Diluted net loss per share attributable to common shareholders is computed by dividing the diluted net loss attributable to common shareholders by the weighted-average number of shares of common shares outstanding for the period, including potential dilutive common shares assuming the dilutive effect of common shares equivalents. In periods in which the Company reports a net loss attributable to common shareholders, the diluted net income (loss) per share attributable to common stockholders is computed by giving effect to all potential dilutive common stock equivalents outstanding for the period determined using the treasury stock method or the if-converted method, as appropriate. For purposes of this calculation, stock options, restricted stock units, restricted stock awards and contingently issuable shares under our Convertible Senior Notes are considered common stock equivalents but have been excluded from the calculation of diluted net loss per share attributable to common stockholders as their effect is anti-dilutive. Emerging Growth Company Status Based on the aggregate worldwide market value of our shares of common stock held by our non-affiliate stockholders as of December 31, 2021, we have become a “large-accelerated filer” and have lost emerging growth status for the year ended December 31, 2021. We are no longer exempt from the auditor attestation requirements of Section 404(b) of the Sarbanes-Oxley Act of 2002, as amended, and our independent registered public accounting firm will evaluate and report on the effectiveness of internal control over financial reporting. Recently Adopted Accounting Pronouncements In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments As a result of this standard, the Company evaluates available-for-sale debt securities under the expected credit loss model. For debt securities with an amortized cost basis in excess of estimated fair value, we determine what amount of that deficit, if any, is caused by expected credit losses. The portion of the deficit attributable to expected credit losses is recognized in other (income) expense, net on our consolidated statements of income. During the twelve months ended December 31, 2021, we did not record any expected credit losses on our available-for-sale debt securities. We adopted the new standard using the modified retrospective approach, which involves recognizing the cumulative effect of initial adoption of Topic 326 as an adjustment to our opening retained earnings as of January 1, 2021. As a result, we did not adjust comparative period financial information for periods before the effective date. No incremental allowance for credit losses has been recognized during the year ended December 31, 2021 as a result of the adoption. The adoption of this standard did not have a material impact on our financial condition, results of operations or disclosures. In 2016, the FASB issued guidance on leases, Accounting Standards Updates 2016-02, Leases quantitative and qualitative disclosures for leasing arrangements and gives rise to other changes impacting certain aspects of lessee and lessor accounting. The two permitted transition methods under the guidance are the modified retrospective transition approach, which requires application of the guidance for all comparative periods, and the cumulative effect adjustment approach, which requires prospective application from the adoption date. The Company adopted ASC 842 effective January 1, 2021 under t |