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		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Pension and other postretirement benefits
Total Other comprehensive income	$ 63	$ 79	$ 159	$ 137
Foreign currency translation adjustments	(852)	(872)	(952)	(563)
Total Other comprehensive (loss) income	(3)		(2)	2
Total Other comprehensive income (loss)	69	134	184	51
Alcoa [Member]
Pension and other postretirement benefits
Balance at beginning of period	(3,968)	(3,477)	(4,063)	(3,533)
Unrecognized net actuarial loss and prior service cost/benefit	(38)	17	(27)	4
Tax benefit (expense)	17	(3)	14
Total Other comprehensive (loss) income before reclassifications, net of tax	(21)	14	(13)	4
Amortization of net actuarial loss and prior service cost/benefit	128	95	260	196
Tax (expense) benefit	(46)	(34)	(91)	(69)
Total amount reclassified from Accumulated other comprehensive loss, net of tax	82	61	169	127
Total Other comprehensive income	61	75	156	131
Balance at end of period	(3,907)	(3,402)	(3,907)	(3,402)
Balance at beginning of period	1,031	1,593	1,147	1,349
Foreign currency translation adjustments	(603)	(685)	(719)	(441)
Balance at end of period	428	908	428	908
Balance at beginning of period	4	2	3
Net unrealized holding (loss) gain	(4)	1	(5)	4
Tax benefit (expense)	2	(1)	2	(2)
Total Other comprehensive (loss) income before reclassifications, net of tax	(2)		(3)	2
Net amount reclassified to earnings			2
Tax (expense) benefit	(1)		(1)
Total amount reclassified from Accumulated other comprehensive income, net of tax	(1)		1
Total Other comprehensive (loss) income	(3)		(2)	2
Balance at end of period	1	2	1	2
Balance at beginning of period	(376)	(524)	(489)	(443)
Net change from periodic revaluations	85	187	221	84
Tax (expense) benefit	(16)	(47)	(45)	(26)
Total Other comprehensive income (loss) before reclassifications, net of tax	69	140	176	58
Net amount reclassified to earnings	1	(5)	8	(6)
Tax (expense) benefit	1	3		5
Total amount reclassified from Accumulated other comprehensive loss, net of tax	2	(2)	8	(1)
Total Other comprehensive income (loss)	71	138	184	57
Balance at end of period	(305)	(386)	(305)	(386)
Alcoa [Member] | Aluminum Contracts [Member]
Pension and other postretirement benefits
Net amount reclassified to earnings		(7)	7	(7)
Alcoa [Member] | Interest Rate Contracts [Member]
Pension and other postretirement benefits
Net amount reclassified to earnings	1	2	1	1
Noncontrolling Interests [Member]
Pension and other postretirement benefits
Balance at beginning of period	(76)	(97)	(77)	(99)
Amortization of net actuarial loss and prior service cost/benefit	4	6	5	8
Tax (expense) benefit	(2)	(2)	(2)	(2)
Total amount reclassified from Accumulated other comprehensive loss, net of tax	2	4	3	6
Total Other comprehensive income	2	4	3	6
Balance at end of period	(74)	(93)	(74)	(93)
Balance at beginning of period	273	416	257	351
Foreign currency translation adjustments	(249)	(187)	(233)	(122)
Balance at end of period	24	229	24	229
Balance at beginning of period	(3)	(6)	(5)	(4)
Net change from periodic revaluations	(3)	(5)		(8)
Tax (expense) benefit	1	1		2
Total Other comprehensive income (loss) before reclassifications, net of tax	(2)	(4)		(6)
Total Other comprehensive income (loss)	(2)	(4)		(6)
Balance at end of period	$ (5)	$ (10)	$ (5)	$ (10)