Acquisitions and Divestitures	6 Months Ended
Jun. 30, 2016
Business Combinations [Abstract]
Acquisitions and Divestitures	E. Acquisitions and Divestitures – In April 2016, Alcoa completed the sale of the Remmele Medical business to LISI MEDICAL for $102 in cash ($99 net of transaction costs), which was included in Proceeds from the sale of assets and businesses on the accompanying Statement of Consolidated Cash Flows. This business, which was part of the RTI International Metals (RTI) acquisition (see below), manufactures precision-machined metal products for customers in the minimally invasive surgical device and implantable device markets. No gain was recorded on this transaction as the excess of the proceeds over the carrying value of the net assets of this business was reflected as a purchase price adjustment (decrease to goodwill of $44) to the preliminary allocation of the purchase price related to Alcoa’s acquisition of RTI. While owned by Alcoa, the operating results and assets and liabilities of this business were included in the Engineered Products and Solutions segment. This business generated sales of approximately $20 from January 1, 2016 through the divestiture date, April 29, 2016, and, at the time of the divestiture, had approximately 330 employees. This transaction is subject to certain post-closing adjustments as defined in the sale agreement. In July 2016, Alcoa’s wholly-owned subsidiary, Alcoa Power Generating Inc., reached an agreement to sell its 215-megawatt Yadkin Hydroelectric Project (Yadkin) to ISQ Hydro Aggregator LLC. Yadkin encompasses four hydroelectric power developments (reservoirs, dams and powerhouses), known as High Rock, Tuckertown, Narrows and Falls, situated along a 38-mile stretch of the Yadkin River through the central part of North Carolina. This transaction is expected to close in the second half of 2016, subject to customary federal and state regulatory approvals. The power generated by Yadkin is primarily sold into the open market. Yadkin generated sales of approximately $20 in 2015, and had approximately 35 employees as of June 30, 2016. The carrying value of the net assets to be sold was $128 and $127 as of June 30, 2016 and December 31, 2015, respectively, which consist mostly of properties, plants, and equipment. In March 2015, Alcoa completed the acquisition of an aerospace structural castings company, TITAL, for $204 (€188) in cash (an additional $1 (€1) was paid in September 2015 to settle working capital in accordance with the purchase agreement). TITAL, a privately held company with approximately 650 employees based in Germany, produces aluminum and titanium investment casting products for the aerospace and defense markets. The purpose of this acquisition is to capture increasing demand for advanced jet engine components made of titanium, establish titanium-casting capabilities in Europe, and expand existing aluminum casting capacity. The assets, including the associated goodwill, and liabilities of this business were included within Alcoa’s Engineered Products and Solutions segment since the date of acquisition. Based on the preliminary allocation of the purchase price, goodwill of $118 was recorded for this transaction. In the first quarter of 2016, the allocation of the purchase price was finalized, based, in part, on the completion of a third-party valuation of certain assets acquired, resulting in a $1 reduction of the initial goodwill amount. None of the $117 in goodwill is deductible for income tax purposes and no other intangible assets were identified. This transaction is no longer subject to post-closing adjustments. In July 2015, Alcoa completed the acquisition of RTI, a global supplier of titanium and specialty metal products and services for the commercial aerospace, defense, energy, and medical device markets, for $870 in Alcoa common stock. The preliminary allocation of the purchase price resulted in total assets of $1,752, including $240 in goodwill and $73 in intangibles, $822 in total liabilities, and $60 in additional capital. In the 2016 six-month period, Alcoa updated the estimated beginning balances of certain assets acquired, including a decrease to each of properties, plants, and equipment of $110, inventories of $48, and intangible assets of $33 and an increase to goodwill of $54. These changes were based, in part, on management’s review of information from a preliminary third-party valuation and the sale of the medical device business (see above). The current allocation of the purchase price, which will be finalized in the third quarter of 2016, is subject to change upon further review by management.

E. Acquisitions and Divestitures – In April 2016, Alcoa completed the sale of the Remmele Medical business to LISI MEDICAL for $102 in cash ($99 net of transaction costs), which was included in Proceeds from the sale of assets and businesses on the accompanying Statement of Consolidated Cash Flows. This business, which was part of the RTI International Metals (RTI) acquisition (see below), manufactures precision-machined metal products for customers in the minimally invasive surgical device and implantable device markets. No gain was recorded on this transaction as the excess of the proceeds over the carrying value of the net assets of this business was reflected as a purchase price adjustment (decrease to goodwill of $44) to the preliminary allocation of the purchase price related to Alcoa’s acquisition of RTI. While owned by Alcoa, the operating results and assets and liabilities of this business were included in the Engineered Products and Solutions segment. This business generated sales of approximately $20 from January 1, 2016 through the divestiture date, April 29, 2016, and, at the time of the divestiture, had approximately 330 employees. This transaction is subject to certain post-closing adjustments as defined in the sale agreement.

In July 2016, Alcoa’s wholly-owned subsidiary, Alcoa Power Generating Inc., reached an agreement to sell its 215-megawatt Yadkin Hydroelectric Project (Yadkin) to ISQ Hydro Aggregator LLC. Yadkin encompasses four hydroelectric power developments (reservoirs, dams and powerhouses), known as High Rock, Tuckertown, Narrows and Falls, situated along a 38-mile stretch of the Yadkin River through the central part of North Carolina. This transaction is expected to close in the second half of 2016, subject to customary federal and state regulatory approvals. The power generated by Yadkin is primarily sold into the open market. Yadkin generated sales of approximately $20 in 2015, and had approximately 35 employees as of June 30, 2016. The carrying value of the net assets to be sold was $128 and $127 as of June 30, 2016 and December 31, 2015, respectively, which consist mostly of properties, plants, and equipment.

In March 2015, Alcoa completed the acquisition of an aerospace structural castings company, TITAL, for $204 (€188) in cash (an additional $1 (€1) was paid in September 2015 to settle working capital in accordance with the purchase agreement). TITAL, a privately held company with approximately 650 employees based in Germany, produces aluminum and titanium investment casting products for the aerospace and defense markets. The purpose of this acquisition is to capture increasing demand for advanced jet engine components made of titanium, establish titanium-casting capabilities in Europe, and expand existing aluminum casting capacity. The assets, including the associated goodwill, and liabilities of this business were included within Alcoa’s Engineered Products and Solutions segment since the date of acquisition. Based on the preliminary allocation of the purchase price, goodwill of $118 was recorded for this transaction. In the first quarter of 2016, the allocation of the purchase price was finalized, based, in part, on the completion of a third-party valuation of certain assets acquired, resulting in a $1 reduction of the initial goodwill amount. None of the $117 in goodwill is deductible for income tax purposes and no other intangible assets were identified. This transaction is no longer subject to post-closing adjustments.

In July 2015, Alcoa completed the acquisition of RTI, a global supplier of titanium and specialty metal products and services for the commercial aerospace, defense, energy, and medical device markets, for $870 in Alcoa common stock. The preliminary allocation of the purchase price resulted in total assets of $1,752, including $240 in goodwill and $73 in intangibles, $822 in total liabilities, and $60 in additional capital. In the 2016 six-month period, Alcoa updated the estimated beginning balances of certain assets acquired, including a decrease to each of properties, plants, and equipment of $110, inventories of $48, and intangible assets of $33 and an increase to goodwill of $54. These changes were based, in part, on management’s review of information from a preliminary third-party valuation and the sale of the medical device business (see above). The current allocation of the purchase price, which will be finalized in the third quarter of 2016, is subject to change upon further review by management.