Basis of Presentation (Policies)	6 Months Ended
Basis of Presentation (Policies)	Dec. 31, 2017
Accounting Policies [Abstract]
Basis of Presentation	The accompanying unaudited consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America for interim financial information and the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by accounting principles generally accepted in the United States of America for complete financial statements. In the opinion of management, all adjustments, consisting of normal and recurring adjustments, considered necessary for a fair statement of the results are reflected in the interim periods presented. The June 30, 2017 consolidated balance sheet data was derived from audited financial statements, but does not include all of the disclosures required by accounting principles generally accepted in the United States of America. These unaudited consolidated financial statements should be read in conjunction with the consolidated financial statements and footnotes thereto included in Carpenter’s annual report on Form 10-K for the fiscal year ended June 30, 2017 (the “2017 Form 10-K”). Operating results for the three and six months ended December 31, 2017 are not necessarily indicative of the operating results for any future period. As used throughout this report, unless the context requires otherwise, the terms “Carpenter”, the “Company”, “Registrant”, “Issuer”, “we” and “our” refer to Carpenter Technology Corporation. During the six months ended December 31, 2017, the Company changed the presentation of borrowings and repayments made under its revolving credit facility in the consolidated statements of cash flows. Prior year amounts have been reclassified to conform to the six months ended December 31, 2017 presentation.
Earnings per Common Share	The Company calculates basic and diluted earnings per share using the two class method. Under the two class method, earnings are allocated to common stock and participating securities (non-vested restricted shares and units that receive non-forfeitable dividends) according to their participation rights in dividends and undistributed earnings. The earnings available to each class of stock are divided by the weighted average number of outstanding shares for the period in each class. Diluted earnings per share assumes the issuance of common stock for all potentially dilutive share equivalents outstanding.
Inventories	Inventories are valued at the lower of cost or market. Cost for inventories is principally determined using the last-in, first-out (“LIFO”) inventory costing method. The Company also uses the first-in, first-out (“FIFO”) and average cost methods.
Regulatory Environmental Costs	The Company is subject to various federal, state, local and international environmental laws and regulations relating to pollution, protection of public health and the environment, natural resource damages and occupational safety and health. Although compliance with these laws and regulations may affect the costs of the Company’s operations, compliance costs to date have not been material. The Company has environmental remediation liabilities at some of its owned operating facilities and has been designated as a potentially responsible party (“PRP”) with respect to certain third party Superfund waste-disposal sites and other third party-owned sites. The Company accrues amounts for environmental remediation costs that represent management’s best estimate of the probable and reasonably estimable future costs related to environmental remediation.
Contingencies and Commitments	The Company is defending various routine claims and legal actions that are incidental to its business and common to its operations, including those pertaining to product claims, commercial disputes, patent infringement, employment actions, employee benefits, compliance with domestic and foreign laws, personal injury claims and tax issues. Like many other manufacturing companies in recent years, the Company, from time to time, has been named as a defendant in lawsuits alleging personal injury as a result of exposure to chemicals and substances in the workplace such as asbestos. The Company provides for costs relating to these matters when a loss is probable and the amount of the loss is reasonably estimable. The effect of the outcome of these matters on the Company’s future results of operations and liquidity cannot be predicted because any such effect depends on future results of operations and the amount and timing (both as to recording future charges to operations and cash expenditures) of the resolution of such matters. While it is not feasible to determine the outcome of these matters, management believes that the total liability from these matters will not have a material effect on the Company’s financial position, results of operations or cash flows over the long-term. However, there can be no assurance that an increase in the scope of pending matters or that any future lawsuits, claims, proceedings or investigations will not be material to the Company’s financial position, results of operations or cash flows in a particular future quarter or year.
Fair Value Measurements	The fair value hierarchy has three levels based on the inputs used to determine fair value. Level 1 refers to quoted prices in active markets for identical assets or liabilities. Level 2 refers to observable inputs other than quoted prices included in Level 1, such as quoted prices for similar assets or liabilities in active markets; quoted prices for identical or similar assets or liabilities in markets that are not active; or other inputs that are observable or can be corroborated by observable market data. Level 3 refers to unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. This includes certain pricing models, discounted cash flow methodologies and similar techniques that use significant unobservable inputs. Currently, the Company does not use Level 1 and 3 inputs.
Fair Value of Financial Instruments	The Company’s derivative financial instruments consist of commodity forward contracts, foreign currency forward contracts and interest rate swaps. These instruments are measured at fair value using the market method valuation technique. The inputs to this technique utilize information related to foreign exchange rates, commodity prices and interest rates published by third party leading financial news and data providers. This is observable data; however, the valuation of these instruments is not based on actual transactions for the same instruments and, as such, they are classified as Level 2. The Company’s use of derivatives and hedging policies are more fully discussed in Note 10. The Company has currently chosen not to elect the fair value option for any items that are not already required to be measured at fair value in accordance with accounting principles generally accepted in the United States of America.
Business Segments	The Company has two reportable segments, Specialty Alloys Operations (“SAO”) and Performance Engineered Products (“PEP”). The SAO segment is comprised of the Company’s major premium alloy and stainless steel manufacturing operations. This includes operations performed at mills primarily in Reading and Latrobe, Pennsylvania and surrounding areas as well as South Carolina and Alabama. The combined assets of the SAO operations are being managed in an integrated manner to optimize efficiency and profitability across the total system. The PEP segment is comprised of the Company’s differentiated operations. This segment includes the Dynamet titanium business, the Carpenter Powder Products business, the Amega West business, and the Latrobe and Mexico distribution businesses. The businesses in the PEP segment are managed with an entrepreneurial structure to promote flexibility and agility to quickly respond to market dynamics. The Company’s executive management evaluates the performance of these operating segments based on sales, operating income and cash flow generation. Segment operating profit excludes general corporate costs, which include executive and director compensation, and other corporate facilities and administrative expenses not allocated to the segments. The service cost component of the Company’s net pension expense, which represents the estimated cost of future pension liabilities earned associated with active employees, is included in the operating income of the business segments. The residual net pension expense, which is comprised of the expected return on plan assets, interest costs on the projected benefit obligations of the plans and amortization of actuarial gains and losses and prior service costs, is included under the heading “Pension earnings, interest and deferrals”.
Recent Accounting Pronouncements Adopted and Not Yet Applicable or Adopted	Recently Issued Accounting Pronouncements - Adopted in current period In March 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-09, Compensation — Stock Compensation (Topic 718) - Improvements to Employee Share-Based Payment Accounting, which outlines new provisions intended to simplify various aspects related to accounting for share-based payments and their presentation in the financial statements. The update revises requirements in the following areas: income tax consequences, forfeitures and classification on the statement of cash flows. The Company adopted this standard in the quarter ended September 30, 2017. The standard did not have a material impact on the consolidated financial statements of the Company. The amendments requiring recognition of excess tax benefits and tax deficiencies in the income statement will be applied prospectively. The inclusion of excess tax benefits and deficiencies as a component of income tax expense will increase volatility of the provision for income taxes as the amount of excess tax benefits or deficiencies from share-based compensation awards are dependent on the stock price at the date the awards are exercised or vested. The Company does not expect the impact to be material to the Company’s consolidated results of operations; however, such determination is subject to change based on facts and circumstances at the time when awards vest or settle. The Company accounts for forfeitures of share-based awards when they occur. The Company applied the amendments related to the presentation of excess tax benefits on the consolidated statement of cash flows using a prospective transition method, and as a result, excess tax benefits related to share-based awards will be reported as cash flows from operating activities. The Company applied the amendments related to the presentation of statutory tax withholding on the consolidated statement of cash flows using a retrospective transition method as required, and as a result, statutory tax withholding related to share-based awards which had been previously classified as cash flows used for operating activities has been be reclassified as cash flows used for financing activities. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230) - Classification of Certain Cash Receipts and Cash Payments, which outlines new provisions intended to reduce the existing diversity in practice related to accounting for the cash flow and its presentation in the financial statements. ASU 2016-15 is effective for public business entities for annual periods, including interim periods within those annual periods, beginning after December 15, 2017, with early adoption permitted. The Company adopted the provisions of ASU 2016-15 in the quarter ended September 30, 2017. The adoption of ASU 2016-15 did not materially impact the Company’s consolidated statement of cash flows. In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows (Topic 230) - Restricted Cash, which outlines that a statement of cash flows explains the change during the period in total cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. ASU 2016-18 is effective for public business entities for annual periods, including interim periods within those annual periods, beginning after December 15, 2017, with early adoption permitted. The Company adopted the provisions of ASU 2016-18 in the quarter ended September 30, 2017. The adoption of ASU 2016-18 did not materially impact the Company’s consolidated statement of cash flows. In January 2017, the FASB issued ASU 2017-04, Intangibles - Goodwill and Other (Topic 350) - Simplifying the Test for Goodwill Impairment, which outlines updates to simplify the subsequent measurement of goodwill by eliminating Step 2 from the goodwill impairment test. ASU 2017-04 is effective for public business entities for annual periods, including interim periods within those annual periods, beginning after December 15, 2019, with early adoption permitted. The Company adopted ASU 2017-04 in the quarter ended September 30, 2017. The adoption of ASU 2017-04 did not have an impact on the Company’s financial statements. Recently Issued Accounting Pronouncements - Pending Adoption In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606). The guidance in ASU 2014-09 requires that an entity 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. The guidance in ASU 2014-09 permits two methods of adoption: full retrospective in which the standard is applied to all of the periods presented or modified retrospective where an entity would recognize the cumulative effect of initially applying the standard as an adjustment to the opening balance of retained earnings. The adoption will include updates as provided under ASU 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net); ASU 2016-10, Revenue from Contracts with Customers: Identifying Performance Obligations and Licensing; ASU 2016-12, Revenue from Contracts with Customers: Narrow-Scope Improvements and Practical Expedients; ASU 2016-20, Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers; ASU 2017-13, Revenue Recognition (Topic 605), Revenue from Contracts with Customers (Topic 606), Leases (Topic 840), and Leases (Topic 842): Amendments to SEC Paragraphs Pursuant to the Staff Announcement at the July 20, 2017 EITF Meeting and Rescission of Prior SEC Staff Announcements and Observer Comments and ASU 2017-14, Income Statement-Reporting Comprehensive Income (Topic 220), Revenue Recognition (Topic 605), and Revenue from Contracts with Customers (Topic 606). The Company is in the process of evaluating the effect that Topic 606 will have on its Consolidated Financial Statements and related disclosures, as well as the expected method of adoption. Currently, the Company is in the process of completing the assessment phase of its evaluation. The assessment phase includes conducting and evaluating the results of internal surveys of its businesses, holding revenue recognition workshops with commercial and business unit finance leadership, and reviewing revenue arrangements across all businesses to initially identify a set of applicable qualitative revenue recognition changes related to the standards update. The Company’s method of adoption for Topic 606 has not yet been determined and is not expected to be finalized until the assessment phase of the evaluation has been completed. The Company’s effective date for the adoption of Topic 606 is July 1, 2018. In February 2016, the FASB issued ASU 2016-02 Leases (Topic 842). ASU 2016-02 improves transparency and comparability among companies by recognizing lease assets and lease liabilities on the balance sheet and by disclosing key information about leasing arrangements. ASU 2016-02 is effective for public business entities for annual periods, including interim periods within those annual periods, beginning after December 15, 2018, with early adoption permitted. The Company is evaluating the impact of the adoption of ASU 2016-02 on the consolidated financial statements. In October 2016, the FASB issued ASU 2016-16, Income Taxes (Topic 740) - Intra-Entity Transfers of Assets Other Than Inventory, which outlines updates to improve the accounting for the income tax consequences of intra-entity transfers of assets other than inventory. ASU 2016-16 is effective for public business entities for annual periods, including interim periods within those annual periods, beginning after December 15, 2017, with early adoption permitted. The Company is evaluating the impact of the adoption of ASU 2016-16 on the consolidated financial statements. In March 2017, the FASB issued ASU 2017-07, Compensation - Retirement Benefits (Topic 715) - Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost, which outlines updates to improve the presentation of net periodic pension cost and net periodic postretirement benefit cost. ASU 2017-07 is effective for public business entities for annual periods, including interim periods within those annual periods, beginning after December 15, 2017, with early adoption permitted. The Company is evaluating the impact of the adoption of ASU 2017-07 on the consolidated financial statements. In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities, which expands and refines hedge accounting for both financial and non-financial risk components, aligns the recognition and presentation of the effects of hedging instruments and hedge items in the financial statements, and includes certain targeted improvements to ease the application of current guidance related to the assessment of hedge effectiveness. ASU 2017-12 is effective for public business entities for annual periods, including interim periods within those annual periods, beginning after December 15, 2018, with early adoption permitted. The Company is evaluating the impact of the adoption of ASU 2017-12 on the consolidated financial statements.