Joint Ventures	6 Months Ended
Joint Ventures	Jun. 30, 2019
Equity Method Investments and Joint Ventures [Abstract]
Joint Ventures	Joint Ventures The financial results of majority-owned joint ventures are consolidated into the Company’s operating results and financial position, with the minority ownership interest recognized in the consolidated statement of income as net income attributable to noncontrolling interests, and as equity attributable to the noncontrolling interests within total stockholders’ equity. Investments in which the Company exercises significant influence, but which it does not control (generally a 20% to 50% ownership interest), are accounted for under the equity method of accounting. Majority-Owned Joint Ventures The Company has a 60% interest in the Chinese joint venture known as Shanghai STAL Precision Stainless Steel Company Limited (STAL). The remaining 40% interest in STAL is owned by China Baowu Steel Group Corporation Limited, a state authorized investment company whose equity securities are publicly traded in the People’s Republic of China. STAL is part of ATI’s FRP segment, and manufactures Precision Rolled Strip stainless products mainly for the electronics, communication equipment, computer and automotive markets located in Asia. Cash and cash equivalents held by STAL as of June 30, 2019 were $45.5 million. The Company has a 51% interest in Next Gen Alloys LLC, a joint venture with GE Aviation for the development of a new meltless titanium alloy powder manufacturing technology. The titanium alloy powders are being developed for use in additive manufacturing applications, including 3D printing. Cash and cash equivalents held by this joint venture as of June 30, 2019 were $6.9 million. During the first quarter 2018, the Company received $2.7 million for the sale of noncontrolling interest related to Next Gen Alloys LLC, which is reported as a financing activity on the consolidated statements of cash flows. Equity Method Joint Ventures On March 1, 2018, the Company announced the formation of the Allegheny & Tsingshan Stainless (A&T Stainless) joint venture with an affiliate company of Tsingshan Group (Tsingshan) to produce 60-inch wide stainless sheet products for sale in North America. Tsingshan purchased a 50% joint venture interest in A&T Stainless for $17.5 million, of which $12.0 million was received in the first six months of 2018 and reported as a financing activity on the consolidated statements of cash flows. The A&T Stainless operations include the Company’s previously-idled direct roll and pickle (DRAP) facility in Midland, PA. ATI provides hot-rolling conversion services to A&T Stainless using the FRP segment’s Hot-Rolling and Processing Facility. As a result of this sale of a 50% noncontrolling interest and the subsequent deconsolidation of the A&T Stainless entity, the Company recognized a $15.9 million gain during the first quarter of 2018 under deconsolidation and derecognition accounting guidance covering the loss of control of a subsidiary determined to be a business. The gain, including ATI’s retained 50% share, was based on the fair value of the joint venture, as determined by the cash purchase price for the noncontrolling interest, and is reported in other income, net on the consolidated statement of income, and is excluded from FRP segment results. Following this deconsolidation, ATI accounts for the A&T Stainless joint venture under the equity method of accounting. ATI’s share of A&T Stainless results were losses of $4.0 million and $7.3 million for the three and six months ended June 30, 2019, respectively, and income of $1.1 million and $0.5 million for the three and six months ended June 30, 2018, respectively, which is included in the FRP segment’s operating results, and within other income, net, on the consolidated statements of income. In late March 2018, ATI filed for an exclusion from the Section 232 tariffs on behalf of A&T Stainless, which imports semi-finished stainless slab products from Indonesia. On April 24, 2019, the Company learned that this exclusion request was denied by the U.S. Department of Commerce. Therefore, the joint venture will continue to be subject to the 25% tariff levied on its imports of semi-finished stainless slab products from Indonesia. Results of A&T Stainless have been and will continue to be negatively impacted by these tariffs on imported stainless slab products. As of June 30, 2019, working capital advances to A&T Stainless were $43.8 million and are reported in prepaid expenses and other current assets on the consolidated balance sheet. ATI’s equity method investment in A&T Stainless at June 30, 2019 was $3.7 million and is reported as part of other long-term assets on the consolidated balance sheet. These balances were evaluated for impairment, as the tariff exclusion denial represents a potential impairment indicator. No impairment exists at this time. The joint venture partners continue to evaluate longer-term solutions to return this strategic initiative to profitability. ATI has a 50% interest in the industrial titanium joint venture known as Uniti LLC (Uniti), with the remaining 50% interest held by VSMPO, a Russian producer of titanium, aluminum, and specialty steel products. Uniti is accounted for under the equity method of accounting. ATI’s share of Uniti’s income was $0.5 million and $1.0 million for the three and six months ended June 30, 2019, respectively, and $1.3 million and $1.8 million for the three and six months ended June 30. 2018, respectively, which is included in the FRP segment’s operating results, and within other income, net on the consolidated statements of income.