Accumulated other Comprehensive Income - Summary of Changes in Accumulated Other Comprehensive Loss by Component (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Pension and other postretirement benefits
Total Other comprehensive income (loss)	$ 557	$ (507)	$ (652)
Foreign currency translation
Other comprehensive loss	(1,335)	(296)	(708)
Available-for-sale-securities
Other comprehensive (loss) income	(1)	2
Cash flow hedges
Total Other comprehensive income (loss)	184	(47)	179
Alcoa [Member]
Pension and other postretirement benefits
Balance at beginning of period	(4,063)	(3,534)	(2,941)
Unrecognized net actuarial loss and prior service cost/benefit	281	(1,184)	(1,159)
Tax (expense) benefit	(88)	398	399
Total Other comprehensive income (loss) before reclassifications, net of tax	193	(786)	(760)
Amortization of net actuarial loss and prior service cost/benefit	520	396	257
Tax (expense) benefit	(182)	(139)	(90)
Total amount reclassified from Accumulated other comprehensive loss, net of tax	338	257	167
Total Other comprehensive income (loss)	531	(529)	(593)
Balance at end of period	(3,532)	(4,063)	(3,534)
Foreign currency translation
Balance at beginning of period	1,147	1,349	1,892
Other comprehensive loss	(968)	(202)	(543)
Balance at end of period	179	1,147	1,349
Available-for-sale-securities
Balance at beginning of period	3	1	1
Other comprehensive (loss) income	(1)	2
Balance at end of period	2	3	1
Cash flow hedges
Balance at beginning of period	(489)	(443)	(627)
Net change from periodic revaluations	205	(2)	88
Tax (expense) benefit	(43)	(10)	(25)
Total Other comprehensive income (loss) before reclassifications, net of tax	162	(12)	63
Net amount reclassified to earnings	(22)	62	(167)
Tax (expense) benefit	(3)	28	(46)
Total amount reclassified from Accumulated other comprehensive loss, net of tax	19	(34)	121
Total Other comprehensive income (loss)	181	(46)	184
Balance at end of period	(308)	(489)	(443)
Alcoa [Member] | Aluminum Contracts [Member]
Cash flow hedges
Net amount reclassified to earnings	18	(65)	152
Alcoa [Member] | Energy Contracts [Member]
Cash flow hedges
Net amount reclassified to earnings			13
Alcoa [Member] | Foreign Exchange Contracts [Member]
Cash flow hedges
Net amount reclassified to earnings	2		(3)
Alcoa [Member] | Interest Rate Contracts [Member]
Cash flow hedges
Net amount reclassified to earnings	2	3	5
Noncontrolling Interests [Member]
Pension and other postretirement benefits
Balance at beginning of period	(77)	(99)	(40)
Unrecognized net actuarial loss and prior service cost/benefit	28	15	(97)
Tax (expense) benefit	(9)	(4)	32
Total Other comprehensive income (loss) before reclassifications, net of tax	19	11	(65)
Amortization of net actuarial loss and prior service cost/benefit	11	16	9
Tax (expense) benefit	(4)	(5)	(3)
Total amount reclassified from Accumulated other comprehensive loss, net of tax	7	11	6
Total Other comprehensive income (loss)	26	22	(59)
Balance at end of period	(51)	(77)	(99)
Foreign currency translation
Balance at beginning of period	257	351	516
Other comprehensive loss	(367)	(94)	(165)
Balance at end of period	(110)	257	351
Cash flow hedges
Balance at beginning of period	(5)	(4)	1
Net change from periodic revaluations	4	(1)	(8)
Tax (expense) benefit	(1)		2
Total Other comprehensive income (loss) before reclassifications, net of tax	3	(1)	(6)
Net amount reclassified to earnings			(1)
Total amount reclassified from Accumulated other comprehensive loss, net of tax			1
Total Other comprehensive income (loss)	3	(1)	(5)
Balance at end of period	(2)	(5)	(4)
Noncontrolling Interests [Member] | Interest Rate Contracts [Member]
Cash flow hedges
Net amount reclassified to earnings			$ 1