Summary of Significant Accounting Policies	3 Months Ended
Summary of Significant Accounting Policies	Dec. 31, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Interim Financial Statements The accompanying unaudited consolidated financial statements have been prepared in accordance with United States generally accepted accounting principles (“U.S. GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all the information and notes required by U.S. GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation have been included. Operating results for the three months ended December 31, 2020 are not necessarily indicative of the results that may be expected for the fiscal year ending September 30, 2021. The consolidated balance sheet at September 30, 2020 has been derived from the audited consolidated financial statements at that date but does not include all the information and notes required by U.S. GAAP for complete financial statements. For further information, refer to the consolidated financial statements and notes thereto included in our Annual Report on Form 10-K for the fiscal year ended September 30, 2020 (File No. 001-32502). Basis of Consolidation The accompanying financial statements present the consolidated accounts of all entities in which the Company has a controlling voting interest and/or variable interest required to be consolidated in accordance with U.S. GAAP. All intercompany balances and transactions have been eliminated. Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 810, Consolidation (“ASC 810”) requires the Company first evaluate its investments to determine if any investments qualify as a variable interest entity (“VIE”). A VIE is consolidated if the Company is deemed to be the primary beneficiary of the VIE, which is the party involved with the VIE that has both (i) the power to control the most significant activities of the VIE and (ii) either the obligation to absorb losses or the right to receive benefits that could potentially be significant to the VIE. If an entity is not deemed to be a VIE, the Company consolidates the entity if the Company has a controlling voting interest. The Company maintains a 52-53 week fiscal year ending on the last Friday in each reporting period. As such, all references to December 31, 2020 and December 31, 2019 relate to the periods ended December 25, 2020 and December 27, 2019, respectively. For convenience purposes, the Company continues to date its first-quarter financial statements as of December 31. The fiscal year ended September 30, 2020 ended on September 25, 2020. The Company has performed a review of all subsequent events through the date the financial statements were issued and has determined that no additional disclosures are necessary. Common Stock On February 28, 2020, the Company amended its certificate of incorporation to increase its authorized capital stock to 2,100,000,000 shares, consisting of 1,000,000,000 shares of Class A Common Stock, 1,000,000,000 shares of Class B Common Stock, and 100,000,000 shares of preferred stock, par value $1.00 per share. In addition, the February 28, 2020 amendment to the Company’s certificate of incorporation also gave effect to the reclassification and 477,242.614671815-for-1 stock split of the Company’s existing common stock outstanding into 510,000,000 shares of Class B Common Stock. This stock split has been retrospectively presented throughout the interim financial statements. Upon completion of the IPO and the exercise in full of the underwriters’ option to purchase additional shares, 88,550,000 shares of Class A Common Stock, 421,450,000 shares of Class B Common Stock and no shares of preferred stock were outstanding. In connection with the IPO, the Company’s board of directors and stockholders approved the Warner Music Group Corp. 2020 Omnibus Incentive Plan, or the “Omnibus Incentive Plan.” The aggregate number of shares of common stock available for issuance under the Omnibus Incentive Plan is 31,169,099 shares of Class A Common Stock over the 10-year period from the date of adoption, including up to 1,000,000 shares of our Class A Common Stock in connection with the IPO. Since the IPO, a total of 30,914 shares of restricted stock has been issued under the Omnibus Incentive Plan to the Company’s directors, which includes 2,553 issued during the three months ended December 31, 2020. Refer to “Stock-Based Compensation” below regarding additional shares issued under our Omnibus Incentive Plan. In connection with the Company’s Senior Management Cash Flow Plan (“the Plan”), equity units held by certain participants were required to be settled in December 2020. This resulted in the redemption of Class A and Class B units held by certain participants in WMG Management Holdings, LLC (“Management LLC”) in exchange for 18,265,813 shares of Class B Common Stock. These shares of Class B Common Stock converted to shares of Class A Common Stock upon exchange. Additionally, the Company issued a total of 4,321,259 additional shares of Class A Common Stock to settle the participants’ remaining deferred equity units previously issued under the Plan. As a result of these transactions, the participants received a total of 22,586,442 shares of Class A Common Stock in connection with the final settlement in December 2020 for all interests previously issued under the Plan. Earnings per Share The consolidated statements of operations present basic and diluted earnings per share (“EPS”). Prior to the completion of the IPO, basic and diluted earnings per share were computed by dividing net income available to common stockholders by the weighted average number of outstanding common shares less shares issued for the exercise of the deferred equity units since these units were mandatorily redeemable in cash. As such, the deferred equity units were excluded from the denominator of the basic and diluted EPS calculation prior to the IPO completion. Subsequent to the completion of the IPO, the Company utilizes the two-class method to report earnings per share. The two-class method is an earnings allocation formula that determines earnings per share for each class of common stock according to dividends declared and participation rights in undistributed earnings. Undistributed earnings allocated to participating securities are subtracted from net income in determining net income attributable to common stockholders. Stock-Based Compensation The Company accounts for stock-based payments as required by ASC 718, Compensation—Stock Compensation (“ASC 718”). Under the recognition provision of ASC 718, the Company’s liability classified stock-based compensation costs are measured each reporting date until settlement. In February 2020, the Company filed a Form S-1 registration statement with the SEC in connection with the IPO, which required a change in accounting policy during the three months ended March 31, 2020 from the intrinsic value method to fair value method in determining the basis of measurement of its stock-based compensation liability. Upon completion of the IPO in June 2020, the Plan was amended to remove the cash-settlement feature on all future redemptions. As a result, all awards previously issued under the Plan required settlement in equity. The participants in such plan were also allowed to sell a pro rata portion, consistent with Access’s percentage reduction in shares of Class B Common Stock as a result of the IPO, of their vested profits interests and acquired units of Management LLC, in the IPO through a “tag-along right.” Under the provision of ASC 718, the Company determined the Plan was modified as of June 3, 2020, and as such, converted the awards from liability-classified to equity-classified. Prior to conversion, the Company performed a final measurement of its stock-based compensation liability under the fair value method. Subsequent to the amendment, the awards issued under the Plan will no longer be adjusted for changes in the value of the Company’s common stock. The Company will continue to incur non-cash stock-based compensation expense for awards that were unvested as of the modification date of the Plan and awards issued under the Omnibus Incentive Plan. During the three months ended December 31, 2020, the Company approved the issuance of restricted stock units (“RSUs”) under the Omnibus Incentive Plan to eligible employees and executives. For accounting purposes, vesting of such restricted stock units commenced during the period. The Company recognized approximately $6 million of stock-based compensation expense for the three months ended December 31, 2020, which is included in additional paid-in capital, for its unvested share awards that were granted prior to the IPO and shares issued under the Omnibus Incentive Plan. Income Taxes The Company uses the estimated annual effective tax rate method in computing its interim tax provision. Certain items, including those deemed to be unusual and infrequent are excluded from the estimated annual effective tax rate. In such cases, the actual tax expense or benefit is reported in the same period as the related item. Certain tax effects are also not reflected in the estimated annual effective tax rate, primarily certain changes in the realizability of deferred tax assets and uncertain tax positions. New Accounting Pronouncements Recently Adopted Accounting Pronouncements In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses: Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”). ASU 2016-13 requires that expected credit losses relating to financial assets measured on an amortized cost basis and available-for-sale debt securities be recorded through an allowance for credit losses. ASU 2016-13 limits the amount of credit losses to be recognized for available-for-sale debt securities to the amount by which carrying value exceeds fair value and also requires the reversal of previously recognized credit losses if fair value increases. The Company adopted ASU 2016-13 in the first quarter of fiscal 2021 and this adoption did not have a material impact on the Company’s consolidated financial statements. Accounting Pronouncements Not Yet Adopted In December 2019, the FASB issued ASU 2019-12, Simplifying the Accounting for Income Taxes (“ASU 2019-12”). This ASU eliminates certain exceptions to the general principles in ASC 740, Income Taxes. Specifically, it eliminates the exception to (1) the incremental approach for intraperiod tax allocation when there is a loss from continuing operations, and income or a gain from other items; (2) the requirement to recognize a deferred tax liability for equity method investments when a foreign subsidiary becomes an equity method investment; (3) the ability not to recognize a deferred tax liability for a foreign subsidiary when a foreign equity method investment becomes a subsidiary; and (4) the general methodology for calculating income taxes in an interim period when a year-to-date loss exceeds the anticipated loss for the year. ASU 2019-12 also simplifies U.S. GAAP by making other changes. ASU 2019-12 will be effective for the annual periods beginning after December 15, 2021, and for interim periods beginning after December 15, 2022. Earlier adoption is permitted. The Company is evaluating the impact of the adoption of this standard on its consolidated financial statements.