Segment and Related Information - Schedule of Operating Results, Capital Expenditures and Assets of Alcoa's Reportable Segments (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Segment Adjusted EBITDA	$ 734	$ 2,280	$ 3,071
Depreciation, depletion, and amortization	610	595	640
Equity (loss) income	(154)	9	120
Capital expenditures	521	473
Equity investments	964	1,107
Total assets	12,007	12,217
Operating Segments [Member]
Segment Reporting Information [Line Items]
Total sales	12,201	14,194	13,711
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment sales	1,663	1,735	1,570
Third-Party Sales [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Third-party sales	10,538	12,459	12,141
Alumina [Member]
Segment Reporting Information [Line Items]
Segment Adjusted EBITDA	273	788	1,192
Depreciation, depletion, and amortization	333	312	351
Equity (loss) income	(48)	(39)	4
Capital expenditures	323	320
Equity investments	395	422
Total assets	6,153	5,859
Alumina [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total sales	5,261	5,432	4,927
Alumina [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment sales	1,648	1,708	1,552
Alumina [Member] | Third-Party Sales [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Third-party sales	3,613	3,724	3,375
Aluminum [Member]
Segment Reporting Information [Line Items]
Segment Adjusted EBITDA	461	1,492	1,879
Depreciation, depletion, and amortization	277	283	289
Equity (loss) income	(106)	48	116
Capital expenditures	198	153
Equity investments	569	685
Total assets	5,854	6,358
Aluminum [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total sales	6,940	8,762	8,784
Aluminum [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment sales	15	27	18
Aluminum [Member] | Third-Party Sales [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Third-party sales	$ 6,925	$ 8,735	$ 8,766