Legal Matters and Contingencies	9 Months Ended
Legal Matters and Contingencies	Jun. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
Legal Matters and Contingencies	Legal Matters and Contingencies In the ordinary course of its business, the Company becomes involved in lawsuits, administrative proceedings, government subpoenas, government investigations, stockholder demands, and other disputes, including antitrust, commercial, product liability, intellectual property, regulatory, employment discrimination, and other matters. Significant damages or penalties may be sought from the Company in some matters, and some matters may require years for the Company to resolve. The Company records a reserve for these matters when it is both probable that a liability has been incurred and the amount of the loss can be reasonably estimated. For those matters for which the Company has not recognized a liability, the Company cannot predict the outcome of their impact on the Company as uncertainty remains with regard to whether such matters will proceed to trial, whether settlements will be reached, and the amount and terms of any such settlements. Outcomes may include settlements in significant amounts that are not currently estimable, limitations on the Company's conduct, the imposition of corporate integrity agreement obligations, consent decrees, and/or other civil and criminal penalties. From time to time, the Company is also involved in disputes with its customers, which the Company generally seeks to resolve through commercial negotiations. If negotiations are unsuccessful, the parties may litigate the dispute or otherwise attempt to settle the matter. With respect to the specific legal proceedings and claims described below, unless otherwise noted, the amount or range of possible losses is not reasonably estimable. There can be no assurance that the settlement, resolution, or other outcome of one or more matters, including the matters set forth below, during any subsequent reporting period will not have a material adverse effect on the Company's results of operations or cash flows for that period or on the Company's financial condition. Opioid Lawsuits and Investigations A significant number of counties, municipalities, and other governmental entities in a majority of U.S. states and Puerto Rico, as well as numerous states and tribes, have filed lawsuits in various federal, state and other courts against pharmaceutical wholesale distributors (including the Company and certain subsidiaries, such as AmerisourceBergen Drug Corporation ("ABDC") and H.D. Smith), pharmaceutical manufacturers, retail chains, medical practices, and physicians relating to the distribution of prescription opioid pain medications. Other lawsuits regarding the distribution of prescription opioid pain medications have been filed by: third-party payors and similar entities; hospitals; hospital groups; and individuals, including cases styled as putative class actions. The lawsuits, which have been and continue to be filed in federal, state, and other courts, generally allege violations of controlled substance laws and various other statutes as well as common law claims, including negligence, public nuisance, and unjust enrichment, and seek equitable relief and monetary damages. An initial group of cases was consolidated for Multidistrict Litigation ("MDL") proceedings before the United States District Court for the Northern District of Ohio (the "Court") in December 2017. Additional cases have been, and will likely continue to be, transferred to the MDL. Further, in June 2018, the Court granted a motion permitting the United States, through the DOJ, to participate in settlement discussions and as a friend of the Court by providing information to facilitate non-monetary remedies. In April 2018, the Court issued an order creating a litigation track, which includes dispositive motion practice, discovery, and trials in certain bellwether jurisdictions. In December 2018, the Court issued an order selecting two additional cases for a second bellwether discovery and trial track. In November 2019 and January 2020, the Court filed Suggestions of Remand with the Judicial Panel on Multidistrict Litigation that identified four cases filed against the Company, including the two additional bellwether cases, for potential transfer from the MDL back to federal courts in California, Oklahoma, and West Virginia for the completion of discovery, motion practice, and trial. All four cases have now been remanded to those federal district courts and discovery has commenced. For the two consolidated cases in West Virginia, the current trial date is October 19, 2020. For the California case, the current trial date is June 28, 2021. No trial date has been established for the Oklahoma case. On October 21, 2019, the Company announced an agreement in principle with two Ohio counties, Cuyahoga and Summit, to settle all claims brought by the two counties against the Company in the first track of the MDL. All claims against the Company were dismissed with prejudice pursuant to the settlement. Pursuant to this settlement, the Company made a payment of $66.7 million in December 2019. The Company had previously recorded a charge of $66.7 million in the fourth quarter of the fiscal year ended September 30, 2019 within Employee Severance, Litigation and Other in its Statement of Operations and in Accrued Expenses and Other on the Company’s Consolidated Balance Sheet. The Court has continued to oversee court-ordered settlement discussions with attorneys for the plaintiffs and certain states that it instituted at the beginning of the MDL proceedings. On October 21, 2019, the Attorneys General for North Carolina, Pennsylvania, Tennessee, and Texas announced certain proposed settlement terms intended to provide a potential framework for a global resolution of the MDL and other related state court litigation, including cases currently filed and that could be filed. The attorneys general's announcement outlined that the largest U.S. pharmaceutical distributors would be expected to pay an aggregate amount of up to $18.0 billion over 18 years, of which the Company's portion would be 31.0%, in addition to the development and participation in a program for free or rebated distribution of opioid-abuse medications for a period of 10 years and the implementation of industry-wide changes to be specified to controlled substance anti-diversion programs. The Company is currently engaged in discussions that include the four attorneys general, as well as other attorneys general, and other parties with the objective of reaching potential terms for a global resolution. The Company is also engaged in related discussions with plaintiffs' lawyers representing local governments and other parties with the same goal of reaching a global resolution with all parties. If agreed, the potential terms for a global resolution would then need to be presented to numerous other states and local governments, and a significant number of such jurisdictions would need to accept the proposed terms in order to achieve an agreement in principle that would provide the finality that the Company requires from a global resolution. Given the large number of parties involved, the complexity and difficulty of the underlying issues, and the resulting uncertainty of achieving a potential global resolution, the Company continues to litigate and prepare for trial in the cases pending in the MDL, those remanded from the MDL to federal district courts, as well as in state courts where lawsuits have been filed, and intends to continue to vigorously defend itself in all such cases. A liability associated with a global resolution has not been recognized as of June 30, 2020, since the Company is unable to predict the outcome of settlement discussions with the states and local governments that will need to participate and, therefore, a global resolution cannot be considered probable. Furthermore, significant uncertainty remains with regard to whether such matters will proceed to trial, and, given the inherent uncertainty related to such litigation, the Company is not in a position to assess the likely outcome, and therefore unable to estimate the range of possible loss. In June 2019, attorneys for some of the plaintiffs filed a motion proposing a procedure to certify a nationwide "negotiation class" of cities and counties for the purpose of negotiating and settling with defendants engaged in the nationwide manufacturing, sale, or distribution of opioids. The attorneys subsequently withdrew the motion and refiled an amended motion on July 9, 2019. The Court granted the motion on September 11, 2019 and certain defendants, including ABDC, are appealing. A trial in New York state for cases brought by Nassau and Suffolk Counties and the New York Attorney General against a variety of defendants, including the Company, was scheduled to begin on March 20, 2020. The trial is not part of the MDL and has been delayed due to the COVID-19 outbreak. The court has not yet set a new trial date but has expressed an intention to commence trial during the fall of 2020, if possible. A trial in Ohio state court for a case brought by the Ohio Attorney General against ABDC and certain other pharmaceutical wholesale distributors is scheduled to begin trial on October 19, 2020. Several other cases filed in various state courts have trial dates scheduled in 2021 and later, although all such dates are subject to change. Aside from those parties that have already filed suit, other entities, including additional attorneys general’s offices, counties, and cities in multiple states, may continue to file additional lawsuits or enforcement proceedings. The Company is vigorously defending itself in the pending lawsuits and intends to vigorously defend itself against any threatened lawsuits or enforcement proceedings. The Company is not in a position to assess the likely outcome or its exposure, if any, with respect to these matters. In addition, other pharmaceutical wholesale distributors have faced shareholder derivative suits alleging violations of fiduciary duties in connection with the oversight of the distribution of controlled substances. The Company has also received subpoenas, civil investigative demands, and other requests for information, requesting the production of documents regarding the distribution of prescription opioid pain medications from government agencies in other jurisdictions, including certain states. The Company is engaged in discussions with representatives from these government agencies regarding the requests and has been producing responsive documents. Since July 2017, the Company has received subpoenas from several U.S. Attorney's Offices, including grand jury subpoenas from the U.S. Attorney's Office for the District of New Jersey ("USAO-NJ") and the U.S. Attorney's Office for the Eastern District of New York ("USAO-EDNY"). Those subpoenas request the production of a broad range of documents pertaining to the Company's distribution of controlled substances through its various subsidiaries, including ABDC, and its diversion control programs. The Company has been engaged in discussions with the various U.S. Attorney’s Offices, including the Health Care and Government Fraud Unit of the Criminal Division of the USAO-NJ, and has been producing documents in response to the subpoenas. Government Enforcement and Related Litigation Matters As previously disclosed, in late January 2020 the Company decided to permanently exit the PharMEDium compounding business. As a result the Company has ceased all commercial operations related to this business as well as all administrative operations other than those needed to complete the shutdown. On May 17, 2019, PharMEDium reached an agreement on the terms of the Consent Decree with the U.S. Food and Drug Administration ("FDA") and the DOJ that was entered by the United States District Court for the Northern District of Illinois on May 22, 2019. PharMEDium remains subject to the terms of the Consent Decree while winding down its operations and continues to work with the FDA and the DOJ to comply with applicable laws and regulations during this process. Subpoenas, Ongoing Investigations, and Other Contingencies From time to time, the Company receives subpoenas or requests for information from various government agencies relating to the Company's business or to the business of a customer, supplier, or other industry participant. The Company's responses often require time and effort and can result in considerable costs being incurred. Most of these matters are resolved without incident; however, such subpoenas or requests can lead to the assertion of claims or the commencement of civil or criminal legal proceedings against the Company and other members of the healthcare industry, as well as to substantial settlements. In January 2017, the Company's subsidiary U.S. Bioservices Corporation ("U.S. Bio") received a subpoena for information from the USAO-EDNY relating to its activities in connection with billing for products and making returns of potential overpayments to government payers. The Company engaged in discussions with the USAO-EDNY and produced documents in response to the subpoena. In April 2019, the government informed the Company that it had filed a notice with the U.S. District Court for the Eastern District of New York that it was declining to intervene in a filed qui tam action related to its investigation. The case was unsealed in April 2019 and counsel for the relator filed an amended complaint under seal with the USAO-EDNY. In December 2019, the government filed a notice that it was again declining to intervene in the action. The court ordered the relator's complaint against the Company, including subsidiaries AmerisourceBergen Specialty Group, LLC and U.S. Bio, be unsealed. The relator’s complaint alleged violations of the federal False Claims Act and the false claims acts of various states. The Company sought leave to file a motion to dismiss relator’s amended complaint. The relator filed a second amended complaint, removing one state false claims act count and the Company renewed its request for leave to file a motion to dismiss the second amended complaint. The court granted the Company's request to file a motion to dismiss and ordered complete briefing on the motion to dismiss, with a response and reply, to be filed with the court on September 28, 2020. On October 11, 2019, Teamsters Local 443 Health Services & Insurance Plan, St. Paul Electrical Construction Pension Plan, St. Paul Electrical Construction Workers Supplemental Pension Plan (2014 Restatement), Retirement Medical Funding Plan for the St. Paul Electrical Workers, and San Antonio Fire & Police Pension Fund filed a complaint for a purported derivative action in the Delaware Court of Chancery against the Company and certain of its current and former officers and directors (collectively, "Defendants"). The complaint alleges that the Defendants breached their fiduciary duties by failing to oversee the compliance by certain of the Company's subsidiaries (including the Company's former subsidiary Medical Initiatives, Inc. ("MII")) with federal regulations, allegedly resulting in the payment of fines and penalties in connection with the settlements with the USAO-EDNY in fiscal 2017 and 2018 that resolved claims arising from MII's pre-filled syringe program. In December 2019, Defendants filed a motion to dismiss the complaint. The motion is fully briefed and remains pending before the Delaware Court of Chancery. On February 6, 2020, Andrea Rosner filed a complaint for a purported derivative action in the United States District Court for the District of Delaware against the Company and certain of its current and former officers and directors. The complaint alleges claims for breach of fiduciary duty, corporate waste and unjust enrichment allegedly arising from the Company’s controlled substance diversion control programs and violation of Section 14(a) of the Securities Exchange Act of 1934. The defendants filed a motion to dismiss this matter on May 4, 2020. On June 30, 2020, Rosner voluntarily dismissed her complaint. On July 17, 2020, CCAR Investments, Inc. filed a complaint for a purported derivative action in the United States District Court for the District of Delaware against the Company and certain of its current and former officers and directors. The complaint alleges claims for breach of fiduciary duty, corporate waste and unjust enrichment allegedly arising from the Company’s controlled substance diversion control programs and violation of Section 14(a) of the Securities Exchange Act of 1934. On July 30, 2020, a group of interested stockholders filed a motion to intervene and stay the proceedings filed by CCAR Investments, Inc. A response to the motion to intervene is due on August 13, 2020. The Company's response to the complaint is expected to be due in mid-August 2020. New York State ("NYS") enacted the Opioid Stewardship Act ("OSA"), which went into effect on July 1, 2018. The OSA established an annual $100 million Opioid Stewardship Fund (the "Fund") and requires manufacturers, distributors, and importers licensed in NYS to ratably source the Fund. The ratable share of the assessment for each licensee was to be based upon opioids sold or distributed to or within NYS. In the fourth quarter of the fiscal year ended September 30, 2018, the Company accrued $22 million as an estimate of its liability under the OSA for opioids distributed from January 1, 2017 through September 30, 2018 and recognized this reserve in Cost of Goods Sold on its Consolidated Statement of Operations and in Accrued Expenses and Other on its Consolidated Balance Sheet as of September 30, 2018. In December 2018, the OSA was ruled unconstitutional by the U.S. District Court for the Southern District of New York, and, as a result, the Company reversed the $22.0 million accrual in the quarter ended December 31, 2018. NYS filed an appeal of the court decision on January 17, 2019; however, the Company does not believe a loss contingency is probable. In December 2019, Reliable Pharmacy, together with other retail pharmacies and North Sunflower Medical Center, filed a civil antitrust complaint against multiple generic drug manufacturers, and also included claims against the Company, H.D. Smith, and other drug distributors and industry participants. The case is filed as a putative class action and plaintiffs purport to represent a class of drug purchasers including other retail pharmacies and healthcare providers. The case has been consolidated for multidistrict litigation proceedings before the United States District Court for the Eastern District of Pennsylvania. The complaint alleges that the Company and others in the industry participated in a conspiracy to fix prices, allocate markets and rig bids regarding generic drugs. In March 2020, the plaintiffs filed a further amended complaint. On July 15, 2020, the Company and other industry participants filed a motion to dismiss the complaint. Litigation Settlements Antitrust Settlements Numerous lawsuits have been filed against certain brand pharmaceutical manufacturers alleging that the manufacturer, by itself or in concert with others, took improper actions to delay or prevent generic drugs from entering the market. These lawsuits are generally brought as class actions. The Company is not typically named as a plaintiff in these lawsuits, but has been a member of the direct purchasers' class (i.e., those purchasers who purchase directly from these pharmaceutical manufacturers). None of the lawsuits have gone to trial, but some have settled in the past with the Company receiving proceeds from the settlement funds. The Company recognized a gain of $8.5 million during the nine months ended June 30, 2020 related to these lawsuits. The Company recognized gains of $3.5 million and $142.7 million during the three and nine months ended June 30, 2019, respectively, related to these lawsuits. These gains, which are net of attorney fees and estimated payments due to other parties, were recorded as reductions to cost of goods sold in the Company’s Consolidated Statements of Operations.