Recently Adopted and Recently Issued Accounting Guidance - Summary of Changes in Accumulated Other Comprehensive Loss by Component (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Pension and other postretirement benefits
Total Other comprehensive income	$ 124	$ 52	$ 283	$ 189
Foreign currency translation adjustments	(36)	238	(988)	(325)
Total Other comprehensive (loss) income	1	2	(1)	4
Total Other comprehensive (loss) income	(49)	(153)	135	(102)
Alcoa [Member]
Pension and other postretirement benefits
Balance at beginning of period	(3,907)	(3,402)	(4,063)	(3,533)
Unrecognized net actuarial loss and prior service cost/benefit	46	(22)	19	(18)
Tax (expense) benefit	(12)	6	2	6
Total Other comprehensive income (loss) before reclassifications, net of tax	34	(16)	21	(12)
Amortization of net actuarial loss and prior service cost/benefit	135	101	395	297
Tax (expense) benefit	(47)	(35)	(138)	(104)
Total amount reclassified from Accumulated other comprehensive loss, net of tax	88	66	257	193
Total Other comprehensive income	122	50	278	181
Balance at end of period	(3,785)	(3,352)	(3,785)	(3,352)
Balance at beginning of period	428	908	1,147	1,349
Foreign currency translation adjustments	(4)	202	(723)	(239)
Balance at end of period	424	1,110	424	1,110
Balance at beginning of period	1	2	3
Net unrealized holding (loss) gain	1	2	(4)	6
Tax (expense) benefit			2	(2)
Total Other comprehensive (loss) income before reclassifications, net of tax	1	2	(2)	4
Net amount reclassified to earnings			2
Tax (expense) benefit			(1)
Total amount reclassified from Accumulated other comprehensive income, net of tax			1
Total Other comprehensive (loss) income	1	2	(1)	4
Balance at end of period	2	4	2	4
Balance at beginning of period	(305)	(386)	(489)	(443)
Net change from periodic revaluations	(70)	(174)	151	(90)
Tax (expense) benefit	14	39	(31)	13
Total Other comprehensive (loss) income before reclassifications, net of tax	(56)	(135)	120	(77)
Net amount reclassified to earnings	8	(31)	16	(37)
Tax (expense) benefit	(2)	13	(2)	18
Total amount reclassified from Accumulated other comprehensive loss, net of tax	6	(18)	14	(19)
Total Other comprehensive (loss) income	(50)	(153)	134	(96)
Balance at end of period	(355)	(539)	(355)	(539)
Alcoa [Member] | Aluminum Contracts [Member]
Pension and other postretirement benefits
Net amount reclassified to earnings	5	(32)	12	(39)
Alcoa [Member] | Foreign Exchange Contracts [Member]
Pension and other postretirement benefits
Net amount reclassified to earnings	3		3
Alcoa [Member] | Interest Rate Contracts [Member]
Pension and other postretirement benefits
Net amount reclassified to earnings		1	1	2
Noncontrolling Interests [Member]
Pension and other postretirement benefits
Balance at beginning of period	(74)	(93)	(77)	(99)
Amortization of net actuarial loss and prior service cost/benefit	2	4	7	12
Tax (expense) benefit		(2)	(2)	(4)
Total amount reclassified from Accumulated other comprehensive loss, net of tax	2	2	5	8
Total Other comprehensive income	2	2	5	8
Balance at end of period	(72)	(91)	(72)	(91)
Balance at beginning of period	24	229	257	351
Foreign currency translation adjustments	(32)	36	(265)	(86)
Balance at end of period	(8)	265	(8)	265
Balance at beginning of period	(5)	(10)	(5)	(4)
Net change from periodic revaluations	2	(1)	2	(9)
Tax (expense) benefit	(1)	1	(1)	3
Total Other comprehensive (loss) income before reclassifications, net of tax	1		1	(6)
Total Other comprehensive (loss) income	1		1	(6)
Balance at end of period	$ (4)	$ (10)	$ (4)	$ (10)