Accumulated Other Comprehensive Loss - Summary of Changes in Accumulated Other Comprehensive Income (Loss) by Component (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Pension and other postretirement benefits
Total Other comprehensive income	$ 15	$ 63	$ 92	$ 159
Foreign currency translation
Other comprehensive income (loss)	200	(852)	536	(952)
Available-for-sale securities
Other comprehensive income (loss)	1	(3)	1	(2)
Cash flow hedges (O)
Total Other comprehensive (loss) income	(31)	69	3	184
Alcoa [Member]
Pension and other postretirement benefits
Balance at beginning of period	(3,455)	(3,968)	(3,532)	(4,063)
Unrecognized net actuarial loss and prior service cost/benefit	(80)	(38)	(63)	(27)
Tax benefit	28	17	25	14
Total Other comprehensive loss before reclassifications, net of tax	(52)	(21)	(38)	(13)
Amortization of net actuarial loss and prior service cost/benefit	101	128	199	260
Tax expense	(35)	(46)	(70)	(91)
Total amount reclassified from Accumulated other comprehensive loss, net of tax	66	82	129	169
Total Other comprehensive income	14	61	91	156
Balance at end of period	(3,441)	(3,907)	(3,441)	(3,907)
Foreign currency translation
Balance at beginning of period	428	1,031	179	1,147
Other comprehensive income (loss)	141	(603)	390	(719)
Balance at end of period	569	428	569	428
Available-for-sale securities
Balance at beginning of period	2	4	2	3
Other comprehensive income (loss)	1	(3)	1	(2)
Balance at end of period	3	1	3	1
Cash flow hedges (O)
Balance at beginning of period	(276)	(376)	(308)	(489)
Net change from periodic revaluations	(32)	85	4	221
Tax benefit (expense)	4	(16)	(4)	(45)
Total Other comprehensive (loss) income before reclassifications, net of tax	(28)	69	0	176
Net amount reclassified to earnings	6	1	11	8
Tax (expense) benefit	(1)	1	(2)	0
Total amount reclassified from Accumulated other comprehensive loss, net of tax	5	2	9	8
Total Other comprehensive (loss) income	(23)	71	9	184
Balance at end of period	(299)	(305)	(299)	(305)
Alcoa [Member] | Aluminum Contracts [Member]
Cash flow hedges (O)
Net amount reclassified to earnings	6	0	11	7
Alcoa [Member] | Foreign Exchange Contracts [Member]
Cash flow hedges (O)
Net amount reclassified to earnings	(1)	0	(1)	0
Alcoa [Member] | Interest Rate Contracts [Member]
Cash flow hedges (O)
Net amount reclassified to earnings	1	1	1	1
Noncontrolling Interests [Member]
Pension and other postretirement benefits
Balance at beginning of period	(51)	(76)	(51)	(77)
Unrecognized net actuarial loss and prior service cost/benefit	0	0	0	0
Tax benefit	0	0	0	0
Total Other comprehensive loss before reclassifications, net of tax	0	0	0	0
Amortization of net actuarial loss and prior service cost/benefit	1	4	2	5
Tax expense		(2)	(1)	(2)
Total amount reclassified from Accumulated other comprehensive loss, net of tax	1	2	1	3
Total Other comprehensive income	1	2	1	3
Balance at end of period	(50)	(74)	(50)	(74)
Foreign currency translation
Balance at beginning of period	(23)	273	(110)	257
Other comprehensive income (loss)	59	(249)	146	(233)
Balance at end of period	36	24	36	24
Available-for-sale securities
Balance at beginning of period	0	0	0	0
Other comprehensive income (loss)	0	0	0	0
Balance at end of period	0	0	0	0
Cash flow hedges (O)
Balance at beginning of period	0	(3)	(2)	(5)
Net change from periodic revaluations	(12)	(3)	(9)	0
Tax benefit (expense)	4	1	3	0
Total Other comprehensive (loss) income before reclassifications, net of tax	(8)	(2)	(6)	0
Net amount reclassified to earnings	0	0	0	0
Tax (expense) benefit	0	0	0	0
Total amount reclassified from Accumulated other comprehensive loss, net of tax	0	0	0	0
Total Other comprehensive (loss) income	(8)	(2)	(6)	0
Balance at end of period	(8)	(5)	(8)	(5)
Noncontrolling Interests [Member] | Aluminum Contracts [Member]
Cash flow hedges (O)
Net amount reclassified to earnings	0	0	0	0
Noncontrolling Interests [Member] | Foreign Exchange Contracts [Member]
Cash flow hedges (O)
Net amount reclassified to earnings	0	0	0	0
Noncontrolling Interests [Member] | Interest Rate Contracts [Member]
Cash flow hedges (O)
Net amount reclassified to earnings	$ 0	$ 0	$ 0	$ 0