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, 2022	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Segment Adjusted EBITDA	$ 2,275	$ 3,053	$ 1,317
Depreciation, depletion, and amortization	595	640	629
Equity (loss) income	9	120	(30)
Capital expenditures	473	380
Equity investments	1,107	1,182
Total assets	12,279	12,066
Operating Segments [Member]
Segment Reporting Information [Line Items]
Total sales	14,920	14,456	11,485
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment sales	2,461	2,315	2,221
Third-Party Sales [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Third-party sales	12,459	12,141	9,264
Bauxite [Member]
Segment Reporting Information [Line Items]
Segment Adjusted EBITDA	82	172	495
Depreciation, depletion, and amortization	130	153	135
Capital expenditures	104	95
Equity investments	188	234
Total assets	1,474	1,430
Bauxite [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total sales	884	947	1,213
Bauxite [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment sales	680	711	941
Bauxite [Member] | Third-Party Sales [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Third-party sales	204	236	272
Alumina [Member]
Segment Reporting Information [Line Items]
Segment Adjusted EBITDA	701	1,002	497
Depreciation, depletion, and amortization	182	198	172
Equity (loss) income	(39)	4	(23)
Capital expenditures	216	178
Equity investments	234	270
Total assets	4,447	4,385
Alumina [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total sales	5,274	4,725	3,895
Alumina [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment sales	1,754	1,586	1,268
Alumina [Member] | Third-Party Sales [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Third-party sales	3,520	3,139	2,627
Aluminum [Member]
Segment Reporting Information [Line Items]
Segment Adjusted EBITDA	1,492	1,879	325
Depreciation, depletion, and amortization	283	289	322
Equity (loss) income	48	116	(7)
Capital expenditures	153	107
Equity investments	685	678
Total assets	6,358	6,251
Aluminum [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total sales	8,762	8,784	6,377
Aluminum [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment sales	27	18	12
Aluminum [Member] | Third-Party Sales [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Third-party sales	$ 8,735	$ 8,766	$ 6,365