Accounting Policies	3 Months Ended
Mar. 31, 2019
Accounting Policies [Abstract]
Accounting Policies	Accounting Policies The interim consolidated financial statements include the accounts of Allegheny Technologies Incorporated and its subsidiaries. Unless the context requires otherwise, “Allegheny Technologies”, “ATI” and “the Company” refer to Allegheny Technologies Incorporated and its subsidiaries. These unaudited consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles for interim financial information and with the instructions for Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and note disclosures required by U.S. generally accepted accounting principles for complete financial statements. In management’s opinion, all adjustments (which include only normal recurring adjustments) considered necessary for a fair presentation have been included. Certain prior year amounts have been reclassified in order to conform with fiscal year 2019 presentation. These unaudited consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto included in the Company’s 2018 Annual Report on Form 10-K. The results of operations for these interim periods are not necessarily indicative of the operating results for any future period. The December 31, 2018 financial information has been derived from the Company’s audited consolidated financial statements. New Accounting Pronouncements Adopted In January 2019, the Company adopted changes issued by the Financial Accounting Standards Board (FASB) related to leases. See Note 7 for further explanation related to this adoption, including all newly expanded disclosure requirements. Pending Accounting Pronouncements In August 2018, the FASB issued new disclosure guidance on fair value measurement. This new guidance modifies the disclosure requirements on fair value measurements, including removal and modifications of various current disclosures as well as some additional disclosure requirements for Level 3 fair value measurements. Some of these disclosure changes must be applied prospectively while others retrospectively depending on requirement. This guidance is required to be adopted by the Company beginning in fiscal year 2020 with early adoption permitted. The Company does not plan to early adopt this guidance. The adoption of these changes is not expected to have an impact on the Company’s consolidated financial statements other than disclosures.

Accounting Policies

The interim consolidated financial statements include the accounts of Allegheny Technologies Incorporated and its subsidiaries. Unless the context requires otherwise, “Allegheny Technologies”, “ATI” and “the Company” refer to Allegheny Technologies Incorporated and its subsidiaries.

These unaudited consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles for interim financial information and with the instructions for Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and note disclosures required by U.S. generally accepted accounting principles for complete financial statements. In management’s opinion, all adjustments (which include only normal recurring adjustments) considered necessary for a fair presentation have been included. Certain prior year amounts have been reclassified in order to conform with fiscal year 2019 presentation. These unaudited consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto included in the Company’s 2018 Annual Report on Form 10-K. The results of operations for these interim periods are not necessarily indicative of the operating results for any future period. The December 31, 2018 financial information has been derived from the Company’s audited consolidated financial statements.

New Accounting Pronouncements Adopted

In January 2019, the Company adopted changes issued by the Financial Accounting Standards Board (FASB) related to leases. See Note 7 for further explanation related to this adoption, including all newly expanded disclosure requirements.

Pending Accounting Pronouncements

In August 2018, the FASB issued new disclosure guidance on fair value measurement. This new guidance modifies the disclosure requirements on fair value measurements, including removal and modifications of various current disclosures as well as some additional disclosure requirements for Level 3 fair value measurements. Some of these disclosure changes must be applied prospectively while others retrospectively depending on requirement. This guidance is required to be adopted by the Company beginning in fiscal year 2020 with early adoption permitted. The Company does not plan to early adopt this guidance. The adoption of these changes is not expected to have an impact on the Company’s consolidated financial statements other than disclosures.