Summary of Significant Accounting Policies	9 Months Ended
Summary of Significant Accounting Policies	Jun. 30, 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 and nine months ended June 30, 2020 are not necessarily indicative of the results that may be expected for the fiscal year ending September 30, 2020. The consolidated balance sheet at September 30, 2019 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, 2019 (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 June 30, 2020 and June 30, 2019 relate to the periods ended June 26, 2020 and June 28, 2019, respectively, except for subsequent event activity referred to in Note 15 and elsewhere. For convenience purposes, the Company continues to date its third-quarter financial statements as of June 30. The fiscal year ended September 30, 2019 ended on September 27, 2019. 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 as of June 30, 2020, 77,000,000 shares of Class A Common Stock were outstanding, 433,000,000 shares of Class B Common Stock were outstanding 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 that would be issued upon vesting of equity awards that we expect to grant, subject to certain conditions, in connection with the IPO. No shares under the Omnibus Incentive Plan have been issued as of June 30, 2020. 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 (loss) per share were computed by dividing net income (loss) 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 (loss) per share. The two-class method is an earnings (loss) allocation formula that determines earnings (loss) per share for each class of common stock according to dividends declared and participation rights in undistributed earnings (losses). Undistributed earnings allocated to participating securities are subtracted from net income in determining net income attributable to common stockholders. Since there was a loss for the three and nine months ended June 30, 2020, no earnings were allocated to our participating securities or our post-modification deferred equity units that are no longer mandatorily redeemable. 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. In determining fair value, the Company utilized an option pricing model for those awards with an option-like pay-off, which includes various inputs for volatility, term to exit, discount for lack of marketability, expected dividend yield and risk-free rates. For awards with an equity-like pay-off, inputs for discount of lack of marketability and non-performance risk were considered. The Company continued to use an income approach using a discounted cash flow model to determine its per-share value input within the model. As a result of this change in accounting policy, the Company recorded a decrease to its stock-based compensation liability of $38 million as of March 31, 2020, which resulted in a decrease of $33 million, net of tax, to accumulated deficit for the nine months ended June 30, 2020. Upon completion of the IPO in June 2020, the Senior Management Free Cash Flow Plan (the “Plan”) was amended to remove the cash-settlement feature on all future redemptions. As a result, all awards previously issued under the Plan will require settlement in Class A Common Stock. 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 the LLC holding company, WMG Management Holdings, LLC (“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, which resulted in non-cash stock-based compensation expense of $437 million recognized in selling, general and administrative expense within our statements of operations for the three and nine months ended June 30, 2020. The final measurement utilized the IPO listing price of $25 per share as the per-share value input within its fair value model. Upon modification of the Plan, the Company reclassified a $769 million stock-based compensation liability to additional-paid in capital, which included $57 million associated with the awards settled through the IPO tag-along right on June 5, 2020. In addition, the Company recognized approximately $3 million of stock-based compensation expense for the period of June 3, 2020 through June 30, 2020 for its unvested share awards that were granted prior to the IPO, which will be recognized over the remaining vesting period based on the fair value under the post-modification terms of the 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 February 2016, the FASB issued ASU 2016-02, Leases (“ASU 2016-02”), which established a new ASC Topic 842 (“ASC 842”) that introduces a right-of-use (“ROU”) model that requires a lessee to record a ROU asset and a lease liability on the balance sheet for all leases with terms longer than 12 months. Leases are classified as either finance or operating, with classification affecting the pattern of expense recognition in the statement of operations. In July 2018, the FASB issued ASU 2018-11, Leases – Targeted Improvements (“ASU 2018-11”), which allows for retrospective application with the recognition of a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. Under this option, entities do not need to apply ASC 842 (along with its disclosure requirements) to the comparative prior periods presented. The Company adopted ASU 2016-02 on October 1, 2019, using the modified retrospective transition method provided by ASU 2018-11. The adoption of ASU 2016-02 resulted in the recognition of operating lease liabilities of $366 million and ROU assets of $297 million, which is net of the historical deferred rent liability balance of $69 million, primarily related to real estate leases. The Company also recorded a decrease to opening accumulated deficit of $7 million, net of taxes, related to previously deferred gains related to sale-leaseback transactions. Upon transition, the Company adopted the “package of three” practical expedient provided by ASC 842 and therefore has not (1) reassessed whether any expired or existing contracts are or contain a lease, (2) reassessed the lease classification for expired or existing leases and (3) reassessed initial direct costs for any existing leases. Rather, the Company will retain the conclusions reached for these items under ASC 840. In August 2017, the FASB issued ASU 2017-12, Targeted Improvements to Accounting for Hedging Activities (“ASU 2017-12”). This ASU improves certain aspects of the hedge accounting model including making more risk management strategies eligible for hedge accounting and simplifying the assessment of hedge effectiveness. ASU 2017-12 is effective for all annual periods beginning after December 15, 2018 and interim periods within those fiscal years. Early adoption is permitted and requires a prospective adoption with a cumulative-effect adjustment to accumulated deficit as of the beginning of the fiscal year of adoption for existing hedging relationships. The Company adopted ASU 2017-12 in the first quarter of fiscal 2020 and this adoption did not have a significant impact on the Company’s financial statements. Accounting Pronouncements Not Yet Adopted 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. ASU 2016-13 will be effective for annual periods beginning after December 15, 2019, and interim periods within those fiscal years. Earlier adoption is permitted. The Company is evaluating the impact of the adoption of this standard on its consolidated financial statements. 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.