Basis of Presentation and Major Accounting Policies	9 Months Ended
Jun. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation and Major Accounting Policies	BASIS OF PRESENTATION AND MAJOR ACCOUNTING POLICIES On September 16, 2015, the Air Products and Chemicals, Inc. (“Air Products”) Board of Directors announced its intention to separate (the “Separation”) Air Products’ Materials Technologies business, into a newly formed company, Versum Materials, LLC. In September 2016, Versum Materials, LLC was converted from a limited liability company to a Delaware corporation, Versum Materials, Inc. On October 1, 2016, Air Products completed the Separation by distributing to its stockholders one share of common stock of Versum for every two shares of Air Products common stock in a distribution intended to be tax-free to Air Products stockholders (the “Distribution”). 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. We are a global business that provides innovative solutions for specific customer applications within niche markets based upon expertise in specialty materials. Our business employs applications technology to provide solutions to the semiconductor industry through chemical synthesis, analytical technology, process engineering, and surface science. We are comprised of two operating segments, Materials and Delivery Systems and Services, under which we manage our operations and assess performance, and a Corporate segment. Basis of Presentation Prior to the Separation the financial statements and information was prepared on a standalone basis and were derived from Air Products’ consolidated financial statements and accounting records where Versum was a division of Air Products. These financial statements reflect the historical basis and carrying values established when the Company was part of Air Products. Subsequent to the Separation, the accompanying Consolidated Financial Statements are presented on a consolidated basis and include all of the accounts and operations of Versum and its majority-owned subsidiaries. The financial statements reflect the financial position, results of operations and cash flows of Versum in accordance with generally accepted accounting principles in the United States of America ("GAAP") for interim financial information. The financial statements are unaudited and should be read in conjunction with the Annual Combined Financial Statements presented in the Company's Annual Report on Form 10-K for our fiscal year ended September 30, 2016. The financial statements reflect all adjustments that, in the opinion of management, are necessary for a fair statement of the results of the interim periods presented; all adjustments of a normal, recurring nature have been included to provide a fair statement of the results for the reporting periods presented. All significant intercompany accounts and transactions have been eliminated. The results of operations for the three and nine months ended June 30, 2017 are not necessarily indicative of the results of operations for the full year. Prior to the Separation, Air Products provided us with centrally managed services and corporate functions. Accordingly, certain shared costs including but not limited to administrative expenses for information technology, general services, human resources, legal, accounting and other services, had been allocated to us and were reflected as expenses in the financial statements. Expenses had been allocated on the basis of direct usage when identifiable, with the remainder allocated on the basis of fixed costs, revenue, operating income or headcount. We consider the expense allocation methodology and results to be reasonable and consistently applied for all periods presented prior to the Separation. After the Separation, Versum has performed most of these functions using its own resources or purchased services. However, the remainder of these functions continue to be provided by Air Products under various agreements. See Note 3, Related Party Transactions and Transactions with Air Products, for a description of the agreements between Versum and Air Products. For periods prior to October 1, 2016, the annual combined balance sheets of Versum included Air Products’ assets and liabilities that were specifically identifiable or were otherwise transferred to us, including subsidiaries and affiliates in which Air Products had a controlling financial interest. Also included within our financial statements were the results of certain product lines which had historically been managed by us but were retained by Air Products after the Separation. Air Products performed cash management and other treasury-related functions on a centralized basis for nearly all of its legal entities. Substantially all cash generated by our business was remitted to Air Products prior to the Separation and therefore accounted for through Air Products’ net investment in the financial statements. Accordingly, Air Products had not allocated any centrally managed cash and cash items to us in the financial statements prior to the Separation. Air Products’ debt and related interest expense had not been allocated to us for any of the periods prior to the Separation since we are not the legal obligor of the debt, and Air Products’ borrowings were not directly attributable to us. There were no other financing arrangements between us and Air Products during the periods presented. For periods prior to the Separation, Versum’s income tax expense was calculated using the separate return method as if Versum was a separate taxpayer. The majority of the accrued U.S. federal, state, and foreign income tax balances were treated as settled with Air Products as of the end of each year. After the Separation, income tax expense and income tax balances represent Versum’s federal, state and foreign income taxes as an independent company. Accounting Policies The policies used in preparing the Consolidated Financial Statements are the same as those used in our Annual Report on Form 10-K for our fiscal year ended September 30, 2016. There have been no significant changes to these accounting policies during the three and nine months ended June 30, 2017. Estimates and Assumptions The Consolidated Financial Statements have been prepared in conformity with GAAP, using management’s best estimates and judgments where appropriate. These estimates and judgments affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements. The estimates and judgments will also affect the reported amounts for certain revenues and expenses during the reporting period. Actual results could differ materially from these estimates and judgments.

BASIS OF PRESENTATION AND MAJOR ACCOUNTING POLICIES

On September 16, 2015, the Air Products and Chemicals, Inc. (“Air Products”) Board of Directors announced its intention to separate (the “Separation”) Air Products’ Materials Technologies business, into a newly formed company, Versum Materials, LLC. In September 2016, Versum Materials, LLC was converted from a limited liability company to a Delaware corporation, Versum Materials, Inc. On October 1, 2016, Air Products completed the Separation by distributing to its stockholders one share of common stock of Versum for every two shares of Air Products common stock in a distribution intended to be tax-free to Air Products stockholders (the “Distribution”). 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.

We are a global business that provides innovative solutions for specific customer applications within niche markets based upon expertise in specialty materials. Our business employs applications technology to provide solutions to the semiconductor industry through chemical synthesis, analytical technology, process engineering, and surface science. We are comprised of two operating segments, Materials and Delivery Systems and Services, under which we manage our operations and assess performance, and a Corporate segment.

Basis of Presentation

Prior to the Separation the financial statements and information was prepared on a standalone basis and were derived from Air Products’ consolidated financial statements and accounting records where Versum was a division of Air Products. These financial statements reflect the historical basis and carrying values established when the Company was part of Air Products. Subsequent to the Separation, the accompanying Consolidated Financial Statements are presented on a consolidated basis and include all of the accounts and operations of Versum and its majority-owned subsidiaries. The financial statements reflect the financial position, results of operations and cash flows of Versum in accordance with generally accepted accounting principles in the United States of America ("GAAP") for interim financial information.

The financial statements are unaudited and should be read in conjunction with the Annual Combined Financial Statements presented in the Company's Annual Report on Form 10-K for our fiscal year ended September 30, 2016. The financial statements reflect all adjustments that, in the opinion of management, are necessary for a fair statement of the results of the interim periods presented; all adjustments of a normal, recurring nature have been included to provide a fair statement of the results for the reporting periods presented. All significant intercompany accounts and transactions have been eliminated. The results of operations for the three and nine months ended June 30, 2017 are not necessarily indicative of the results of operations for the full year.

Prior to the Separation, Air Products provided us with centrally managed services and corporate functions. Accordingly, certain shared costs including but not limited to administrative expenses for information technology, general services, human resources, legal, accounting and other services, had been allocated to us and were reflected as expenses in the financial statements. Expenses had been allocated on the basis of direct usage when identifiable, with the remainder allocated on the basis of fixed costs, revenue, operating income or headcount. We consider the expense allocation methodology and results to be reasonable and consistently applied for all periods presented prior to the Separation.

After the Separation, Versum has performed most of these functions using its own resources or purchased services. However, the remainder of these functions continue to be provided by Air Products under various agreements. See Note 3, Related Party Transactions and Transactions with Air Products, for a description of the agreements between Versum and Air Products.

For periods prior to October 1, 2016, the annual combined balance sheets of Versum included Air Products’ assets and liabilities that were specifically identifiable or were otherwise transferred to us, including subsidiaries and affiliates in which Air Products had a controlling financial interest. Also included within our financial statements were the results of certain product lines which had historically been managed by us but were retained by Air Products after the Separation. Air Products performed cash management and other treasury-related functions on a centralized basis for nearly all of its legal entities. Substantially all cash generated by our business was remitted to Air Products prior to the Separation and therefore accounted for through Air Products’ net investment in the financial statements. Accordingly, Air Products had not allocated any centrally managed cash and cash items to us in the financial statements prior to the Separation. Air Products’ debt and related interest expense had not been allocated to us for any of the periods prior to the Separation since we are not the legal obligor of the debt, and Air Products’ borrowings were not directly attributable to us. There were no other financing arrangements between us and Air Products during the periods presented.

For periods prior to the Separation, Versum’s income tax expense was calculated using the separate return method as if Versum was a separate taxpayer. The majority of the accrued U.S. federal, state, and foreign income tax balances were treated as settled with Air Products as of the end of each year. After the Separation, income tax expense and income tax balances represent Versum’s federal, state and foreign income taxes as an independent company.

Accounting Policies

The policies used in preparing the Consolidated Financial Statements are the same as those used in our Annual Report on Form 10-K for our fiscal year ended September 30, 2016. There have been no significant changes to these accounting policies during the three and nine months ended June 30, 2017.

Estimates and Assumptions

The Consolidated Financial Statements have been prepared in conformity with GAAP, using management’s best estimates and judgments where appropriate. These estimates and judgments affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements. The estimates and judgments will also affect the reported amounts for certain revenues and expenses during the reporting period. Actual results could differ materially from these estimates and judgments.