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Segment Information - Schedule of Segment ATOI to Consolidated Net Income Attributable to Alcoa (Detail) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2015 | Sep. 30, 2014 | Sep. 30, 2015 | Sep. 30, 2014
Segment Reporting Information [Line Items] |  |  |  |
Total segment ATOI | $ 410 | $ 581 | $ 1,633 | $ 1,309
Interest expense | (123) | (126) | (369) | (351)
Noncontrolling interests | (62) | 18 | (189) | 46
Consolidated net income attributable to Alcoa | 44 | 149 | 379 | 109
Other [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Impact of LIFO | 50 | (18) | 93 | (33)
Metal price lag | (48) | 38 | (110) | 56
Interest expense | (80) | (81) | (240) | (228)
Noncontrolling interests | (62) | 18 | (189) | 46
Corporate expense | (72) | (72) | (199) | (204)
Restructuring and other charges | (48) | (189) | (368) | (587)
Other | $ (106) | $ (128) | $ (241) | $ (250)

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