Summary of Significant Accounting Policies	3 Months Ended
Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation The accompanying financial statements present the consolidated financial position, results of operations, and cash flows of AmerisourceBergen Corporation and its wholly-owned subsidiaries (the "Company") as of the dates and for the periods indicated. All intercompany accounts and transactions have been eliminated in consolidation. The accompanying unaudited consolidated financial statements have been prepared in conformity with U.S. generally accepted accounting principles ("GAAP") for interim financial information, the instructions to Form 10-Q, and Rule 10-01 of Regulation S-X. In the opinion of management, all adjustments (consisting only of normal recurring accruals, except as otherwise disclosed herein) considered necessary to present fairly the financial position as of December 31, 2017 and the results of operations and cash flows for the interim periods ended December 31, 2017 and 2016 have been included. Certain information and footnote disclosures normally included in financial statements presented in accordance with U.S. GAAP, but which are not required for interim reporting purposes, have been omitted. The accompanying unaudited consolidated financial statements should be read in conjunction with the financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the fiscal year ended September 30, 2017. The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect amounts reported in the financial statements and accompanying notes. Actual amounts could differ from these estimated amounts. Certain reclassifications have been made to prior period amounts in order to conform to the current year presentation. Recently Issued Accounting Pronouncements Not Yet Adopted In May 2014, the Financial Accounting Standards Board ("FASB") issued ASU No. 2014-09, "Revenue from Contracts with Customers (Topic 606)" ("ASU 2014-09"). ASU 2014-09 supersedes the revenue recognition requirements in Accounting Standards Codification 605 - "Revenue Recognition" and most industry-specific guidance throughout the Codification. ASU 2014-09 outlines a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers. The standard's core principle is that a company should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. ASU 2014-09 was originally scheduled to be effective for annual reporting periods beginning after December 15, 2016, including interim periods within those reporting periods. In July 2015, the FASB deferred the effective date of ASU 2014-09 by one year. In March 2016, the FASB issued ASU No. 2016-08, "Revenue from Contracts with Customers (Topic 606) - Principal versus Agent Considerations" ("ASU 2016-08"), which clarifies the implementation guidance for principal versus agent considerations in ASU 2014-09. In April 2016, the FASB issued ASU No. 2016-10, "Revenue from Contracts with Customers (Topic 606) - Identifying Performance Obligations and Licensing" ("ASU 2016-10"), which amends the guidance in ASU 2014-09 related to identifying performance obligations and accounting for licenses of intellectual property. The Company must adopt ASU 2016-08 and ASU 2016-10 with ASU 2014-09. Entities are permitted to adopt the standards as early as the original public entity effective date of ASU 2014-09, and either full or modified retrospective application is required. The Company continues to evaluate the impact of adopting ASU 2016-08, ASU 2016-10, and ASU 2014-09. It has conducted a preliminary assessment of the Pharmaceutical Distribution Services reportable segment and the operating segments in Other and does not expect adoption of the new standard to have a material impact on its consolidated financial statements. For example, the majority of the Pharmaceutical Distribution Services reportable segment's revenue is generated from sales of pharmaceutical products, which will continue to be recognized when control of goods is transferred to the customer. This preliminary assessment is subject to change prior to adoption. Additionally, the Company expects to adopt this standard in the first quarter of fiscal 2019, and it is still evaluating the method of adoption. In February 2016, the FASB issued ASU No. 2016-02, "Leases (Topic 842)" ("ASU 2016-02"). ASU 2016-02 aims to increase transparency and comparability across organizations by requiring lease assets and lease liabilities to be recognized on the balance sheet as well as key information to be disclosed regarding lease arrangements. ASU 2016-02 is effective for annual reporting periods beginning after December 15, 2018 and interim periods within those fiscal years. Entities are permitted to adopt the standard early, and a modified retrospective application is required. The Company anticipates that the adoption of this new accounting standard will have a material impact on the Company's Consolidated Balance Sheets. However, the Company is continuing to evaluate the impact of adopting this new accounting guidance and, therefore, cannot reasonably estimate the impact on the results of operations or cash flows at this time. As of December 31, 2017, there were no other recently-issued accounting standards that may have a material impact on the Company’s financial position, results of operations, or cash flows upon their adoption.

Summary of Significant Accounting Policies

Basis of Presentation

The accompanying financial statements present the consolidated financial position, results of operations, and cash flows of AmerisourceBergen Corporation and its wholly-owned subsidiaries (the "Company") as of the dates and for the periods indicated. All intercompany accounts and transactions have been eliminated in consolidation.

The accompanying unaudited consolidated financial statements have been prepared in conformity with U.S. generally accepted accounting principles ("GAAP") for interim financial information, the instructions to Form 10-Q, and Rule 10-01 of Regulation S-X. In the opinion of management, all adjustments (consisting only of normal recurring accruals, except as otherwise disclosed herein) considered necessary to present fairly the financial position as of December 31, 2017 and the results of operations and cash flows for the interim periods ended December 31, 2017 and 2016 have been included. Certain information and footnote disclosures normally included in financial statements presented in accordance with U.S. GAAP, but which are not required for interim reporting purposes, have been omitted. The accompanying unaudited consolidated financial statements should be read in conjunction with the financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the fiscal year ended September 30, 2017.

The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect amounts reported in the financial statements and accompanying notes. Actual amounts could differ from these estimated amounts. Certain reclassifications have been made to prior period amounts in order to conform to the current year presentation.

Recently Issued Accounting Pronouncements Not Yet Adopted

In May 2014, the Financial Accounting Standards Board ("FASB") issued ASU No. 2014-09, "Revenue from Contracts with Customers (Topic 606)" ("ASU 2014-09"). ASU 2014-09 supersedes the revenue recognition requirements in Accounting Standards Codification 605 - "Revenue Recognition" and most industry-specific guidance throughout the Codification. ASU 2014-09 outlines a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers. The standard's core principle is that a company should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. ASU 2014-09 was originally scheduled to be effective for annual reporting periods beginning after December 15, 2016, including interim periods within those reporting periods. In July 2015, the FASB deferred the effective date of ASU 2014-09 by one year.

In March 2016, the FASB issued ASU No. 2016-08, "Revenue from Contracts with Customers (Topic 606) - Principal versus Agent Considerations" ("ASU 2016-08"), which clarifies the implementation guidance for principal versus agent considerations in ASU 2014-09. In April 2016, the FASB issued ASU No. 2016-10, "Revenue from Contracts with Customers (Topic 606) - Identifying Performance Obligations and Licensing" ("ASU 2016-10"), which amends the guidance in ASU 2014-09 related to identifying performance obligations and accounting for licenses of intellectual property. The Company must adopt ASU 2016-08 and ASU 2016-10 with ASU 2014-09. Entities are permitted to adopt the standards as early as the original public entity effective date of ASU 2014-09, and either full or modified retrospective application is required.

The Company continues to evaluate the impact of adopting ASU 2016-08, ASU 2016-10, and ASU 2014-09. It has conducted a preliminary assessment of the Pharmaceutical Distribution Services reportable segment and the operating segments in Other and does not expect adoption of the new standard to have a material impact on its consolidated financial statements. For example, the majority of the Pharmaceutical Distribution Services reportable segment's revenue is generated from sales of pharmaceutical products, which will continue to be recognized when control of goods is transferred to the customer. This preliminary assessment is subject to change prior to adoption. Additionally, the Company expects to adopt this standard in the first quarter of fiscal 2019, and it is still evaluating the method of adoption.

In February 2016, the FASB issued ASU No. 2016-02, "Leases (Topic 842)" ("ASU 2016-02"). ASU 2016-02 aims to increase transparency and comparability across organizations by requiring lease assets and lease liabilities to be recognized on the balance sheet as well as key information to be disclosed regarding lease arrangements. ASU 2016-02 is effective for annual reporting periods beginning after December 15, 2018 and interim periods within those fiscal years. Entities are permitted to adopt the standard early, and a modified retrospective application is required. The Company anticipates that the adoption of this new accounting standard will have a material impact on the Company's Consolidated Balance Sheets. However, the Company is continuing to evaluate the impact of adopting this new accounting guidance and, therefore, cannot reasonably estimate the impact on the results of operations or cash flows at this time.

As of December 31, 2017, there were no other recently-issued accounting standards that may have a material impact on the Company’s financial position, results of operations, or cash flows upon their adoption.