Segment and Geographic Area Information - Schedule of Operating Results of Alcoa's Reportable Segment (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Segment Reporting Information [Line Items]
Total sales	$ 6,676	$ 7,159
Equity income (loss)	(38)	(12)
Depreciation, depletion, and amortization	319	341
Income taxes	154	138
After-tax operating income (ATOI)	325	351
Intersegment Sales [Member]
Segment Reporting Information [Line Items]
Intersegment sales	1,287	1,373
Third-Party Sales [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Third-party sales	5,389	5,786
Alumina [Member]
Segment Reporting Information [Line Items]
Total sales	1,355	1,421
Equity income (loss)	(5)	1
Depreciation, depletion, and amortization	97	109
Income taxes	40	14
After-tax operating income (ATOI)	92	58
Alumina [Member] | Intersegment Sales [Member]
Segment Reporting Information [Line Items]
Intersegment sales	510	595
Alumina [Member] | Third-Party Sales [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Third-party sales	845	826
Primary Metals [Member]
Segment Reporting Information [Line Items]
Total sales	2,158	2,485
Equity income (loss)	(28)	(9)
Depreciation, depletion, and amortization	124	135
Income taxes	(11)	1
After-tax operating income (ATOI)	(15)	39
Primary Metals [Member] | Intersegment Sales [Member]
Segment Reporting Information [Line Items]
Intersegment sales	734	727
Primary Metals [Member] | Third-Party Sales [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Third-party sales	1,424	1,758
Global Rolled Products [Member]
Segment Reporting Information [Line Items]
Total sales	1,720	1,830
Equity income (loss)	(5)	(4)
Depreciation, depletion, and amortization	58	57
Income taxes	34	39
After-tax operating income (ATOI)	59	81
Global Rolled Products [Member] | Intersegment Sales [Member]
Segment Reporting Information [Line Items]
Intersegment sales	43	51
Global Rolled Products [Member] | Third-Party Sales [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Third-party sales	1,677	1,779
Engineered Products and Solutions [Member]
Segment Reporting Information [Line Items]
Total sales	1,443	1,423
Depreciation, depletion, and amortization	40	40
Income taxes	91	84
After-tax operating income (ATOI)	189	173
Engineered Products and Solutions [Member] | Third-Party Sales [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Third-party sales	$ 1,443	$ 1,423