Commitments and Contingencies	12 Months Ended
Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	21.COMMITMENTS AND CONTINGENCIES Litigation In the normal course of business, Versum may be involved in various legal proceedings, including commercial, environmental, health, safety, and product liability matters. Although litigation with respect to these matters is routine and incidental to the conduct of our business, such litigation may result in large monetary awards for compensatory and punitive damages. Versum does not currently believe that there are any legal proceedings, individually or in the aggregate, that are reasonably possible to have a material impact on its financial condition, results of operations, or cash flows. Environmental and Regulatory Proceedings From time to time, Versum may be involved in proceedings, investigations, and audits involving governmental authorities in connection with environmental, health, safety, competition, and tax matters. In addition, pursuant to the Separation Agreement, Versum is liable to Air Products for proceedings by the Environmental Protection Agency under the Comprehensive Environmental Response, Compensation, and Liability Act, the federal Superfund law (“CERCLA”); the Resource Conservation and Recovery Act (“RCRA”); and similar state and foreign environmental laws relating to current or former Electronic Materials business sites, and third-party waste disposal facilities used by the Electronic Materials business, that have been designated for investigation or remediation. Versum may be liable for any unknown environmental liabilities related to legacy businesses and sites formerly owned and operated by Air Products related to its former electronics businesses. Versum does not currently believe that there are any environmental or regulatory matters, individually or in the aggregate, that are reasonably possible to have a material impact on our financial condition, results of operations, or cash flows. Any future charges related to the costs of litigation, environmental, or regulatory proceedings for fines, settlements or damages related to any such matters could have a material impact on our results of operations or cash flows in the period incurred. While Versum cannot predict the outcome of any litigation, environmental, or regulatory matter or the potential for future litigation or regulatory action, we have evaluated all litigation, environmental and regulatory proceedings, claims and assessments in which Versum is involved, and do not believe that any of these matters, individually or in the aggregate, will result in losses that are materially in excess of amounts already recognized, if any. Unconditional Purchase Obligations We have unconditional purchase obligations of approximately $44.5 million for plant and equipment purchases as well as R&D facility enhancements. Otherwise, there are no material obligations.

21.COMMITMENTS AND CONTINGENCIES

Litigation

In the normal course of business, Versum may be involved in various legal proceedings, including commercial, environmental, health, safety, and product liability matters. Although litigation with respect to these matters is routine and incidental to the conduct of our business, such litigation may result in large monetary awards for compensatory and punitive damages. Versum does not currently believe that there are any legal proceedings, individually or in the aggregate, that are reasonably possible to have a material impact on its financial condition, results of operations, or cash flows.

Environmental and Regulatory Proceedings

From time to time, Versum may be involved in proceedings, investigations, and audits involving governmental authorities in connection with environmental, health, safety, competition, and tax matters. In addition, pursuant to the Separation Agreement, Versum is liable to Air Products for proceedings by the Environmental Protection Agency under the Comprehensive Environmental Response, Compensation, and Liability Act, the federal Superfund law (“CERCLA”); the Resource Conservation and Recovery Act (“RCRA”); and similar state and foreign environmental laws relating to current or former Electronic Materials business sites, and third-party waste disposal facilities used by the Electronic Materials business, that have been designated for investigation or remediation. Versum may be liable for any unknown environmental liabilities related to legacy businesses and sites formerly owned and operated by Air Products related to its former electronics businesses. Versum does not currently believe that there are any environmental or regulatory matters, individually or in the aggregate, that are reasonably possible to have a material impact on our financial condition, results of operations, or cash flows.

Any future charges related to the costs of litigation, environmental, or regulatory proceedings for fines, settlements or damages related to any such matters could have a material impact on our results of operations or cash flows in the period incurred. While Versum cannot predict the outcome of any litigation, environmental, or regulatory matter or the potential for future litigation or regulatory action, we have evaluated all litigation, environmental and regulatory proceedings, claims and assessments in which Versum is involved, and do not believe that any of these matters, individually or in the aggregate, will result in losses that are materially in excess of amounts already recognized, if any.

Unconditional Purchase Obligations

We have unconditional purchase obligations of approximately $44.5 million for plant and equipment purchases as well as R&D facility enhancements. Otherwise, there are no material obligations.