Subsequent Events	12 Months Ended
Sep. 30, 2016
Subsequent Events [Abstract]
Subsequent Events	On September 29, 2016, Versum entered into a Separation Agreement with Air Products, pursuant to which Air Products sold its Electronic Materials business to Versum and distributed to Air Products stockholders all of the issued and outstanding shares of common stock of Versum on the basis of one-half share of common stock of Versum for each share of Air Products common stock issued and outstanding in a distribution intended to be tax-free to Air Products stockholders. The Distribution, which was effective on October 1, 2016, was made to Air Products stockholders of record as of the close of business on September 21, 2016. As a result of the Distribution, Versum is now an independent public company and its common stock is listed under the symbol “VSM” on the New York Stock Exchange. Our Relationship with Air Products We operate separately as an independent public company. In connection with the Separation and Distribution, on September 29, 2016, Versum and its affiliates entered into various agreements with Air Products and its affiliates contemplated by the Separation Agreement, including the following agreements: Transition Services Agreement. Under the Transition Services Agreement, Air Products provides certain transition services to us and we provide certain transition services to Air Products. Each party provides these services for a limited time, generally for no longer than 12 to 24 months following the October 1, 2016 Distribution date, for specified fees, which are at cost for services provided by third parties and at cost plus approximately 5% percent for services provided by either us or Air Products, as applicable. Tax Matters Agreement. The Tax Matters Agreement generally governs Air Products’ and Versum’s respective rights, responsibilities and obligations with respect to taxes (including taxes arising in the ordinary course of business and taxes, if any, incurred as a result of any failure of the contribution, the Distribution or certain related transactions to qualify as tax-free for U.S. federal income tax purposes), tax attributes, the preparation and filing of tax returns, the control of audits and other tax proceedings and other matters regarding taxes for any tax period ending on or before the Distribution date, as well as tax periods beginning after the Distribution date. In addition, the Tax Matters Agreement imposes certain restrictions on us and our subsidiaries (including restrictions on share issuances, business combinations, sales of assets and similar transactions) designed to preserve the tax-free status of the contribution, the Distribution and certain related transactions. The Tax Matters Agreement includes special rules that allocate tax liabilities in the event the contribution, the Distribution, or certain related transactions fail to qualify as tax-free for U.S. federal income tax purposes. In general, Versum is liable for taxes incurred by Air Products that may arise if Versum takes, or fails to take, as the case may be, certain actions that may result in the contribution, the Distribution or certain related transactions failing to qualify as tax-free for U.S. federal income tax purposes. Employee Matters Agreement. The Employee Matters Agreement governs the compensation and employee benefit obligations with respect to our current and former employees and those of Air Products. The Employee Matters Agreement allocates liabilities and responsibilities relating to employee compensation and benefits plans and programs and other related matters in connection with the Distribution including, without limitation, the treatment of outstanding Air Products’ equity awards, other outstanding incentive compensation awards, deferred compensation obligations and retirement and welfare benefit obligations. In 2017, certain international pension plans were legally split. Currently, the funded status of these shared plans is not reflected on Versum’s annual combined balance sheet as the plans are accounted for as multiemployer plans. Upon legal separation of the plans in 2017 the funded status of Versum’s portion of these plans, which is a net pension liability estimated at approximately $24 million, will be reflected on the balance sheet in the first quarter of 2017. Intellectual Property Agreements. Certain of our subsidiaries entered into agreements with Air Products with respect to intellectual property. A two-way cross-license between Air Products and one of our affiliates requires one of our affiliates to exclusively license to Air Products certain patents for a defined field of use. Correspondingly, Air Products exclusively licensed certain patents to one of our affiliates for a defined field of use. Air Products also granted Versum or one of our affiliates a license under various Engineering Standards developed and owned by it as well as Safety, Health and Environmental Standards and Policies developed and owned by it, for a limited period of time in order to allow us to continue our operations and develop our own Standards and Policies.

On September 29, 2016, Versum entered into a Separation Agreement with Air Products, pursuant to which Air Products sold its Electronic Materials business to Versum and distributed to Air Products stockholders all of the issued and outstanding shares of common stock of Versum on the basis of one-half share of common stock of Versum for each share of Air Products common stock issued and outstanding in a distribution intended to be tax-free to Air Products stockholders. The Distribution, which was effective on October 1, 2016, was made to Air Products stockholders of record as of the close of business on September 21, 2016. As a result of the Distribution, Versum is now an independent public company and its common stock is listed under the symbol “VSM” on the New York Stock Exchange.

Our Relationship with Air Products

We operate separately as an independent public company. In connection with the Separation and Distribution, on September 29, 2016, Versum and its affiliates entered into various agreements with Air Products and its affiliates contemplated by the Separation Agreement, including the following agreements:

Transition Services Agreement. Under the Transition Services Agreement, Air Products provides certain transition services to us and we provide certain transition services to Air Products. Each party provides these services for a limited time, generally for no longer than 12 to 24 months following the October 1, 2016 Distribution date, for specified fees, which are at cost for services provided by third parties and at cost plus approximately 5% percent for services provided by either us or Air Products, as applicable.

Tax Matters Agreement. The Tax Matters Agreement generally governs Air Products’ and Versum’s respective rights, responsibilities and obligations with respect to taxes (including taxes arising in the ordinary course of business and taxes, if any, incurred as a result of any failure of the contribution, the Distribution or certain related transactions to qualify as tax-free for U.S. federal income tax purposes), tax attributes, the preparation and filing of tax returns, the control of audits and other tax proceedings and other matters regarding taxes for any tax period ending on or before the Distribution date, as well as tax periods beginning after the Distribution date. In addition, the Tax Matters Agreement imposes certain restrictions on us and our subsidiaries (including restrictions on share issuances, business combinations, sales of assets and similar transactions) designed to preserve the tax-free status of the contribution, the Distribution and certain related transactions. The Tax Matters Agreement includes special rules that allocate tax liabilities in the event the contribution, the Distribution, or certain related transactions fail to qualify as tax-free for U.S. federal income tax purposes. In general, Versum is liable for taxes incurred by Air Products that may arise if Versum takes, or fails to take, as the case may be, certain actions that may result in the contribution, the Distribution or certain related transactions failing to qualify as tax-free for U.S. federal income tax purposes.

Employee Matters Agreement. The Employee Matters Agreement governs the compensation and employee benefit obligations with respect to our current and former employees and those of Air Products. The Employee Matters Agreement allocates liabilities and responsibilities relating to employee compensation and benefits plans and programs and other related matters in connection with the Distribution including, without limitation, the treatment of outstanding Air Products’ equity awards, other outstanding incentive compensation awards, deferred compensation obligations and retirement and welfare benefit obligations.

In 2017, certain international pension plans were legally split. Currently, the funded status of these shared plans is not reflected on Versum’s annual combined balance sheet as the plans are accounted for as multiemployer plans. Upon legal separation of the plans in 2017 the funded status of Versum’s portion of these plans, which is a net pension liability estimated at approximately $24 million, will be reflected on the balance sheet in the first quarter of 2017.

Intellectual Property Agreements. Certain of our subsidiaries entered into agreements with Air Products with respect to intellectual property. A two-way cross-license between Air Products and one of our affiliates requires one of our affiliates to exclusively license to Air Products certain patents for a defined field of use. Correspondingly, Air Products exclusively licensed certain patents to one of our affiliates for a defined field of use. Air Products also granted Versum or one of our affiliates a license under various Engineering Standards developed and owned by it as well as Safety, Health and Environmental Standards and Policies developed and owned by it, for a limited period of time in order to allow us to continue our operations and develop our own Standards and Policies.