Accumulated Other Comprehensive Loss - Summary of Changes in Accumulated Other Comprehensive Loss by Component (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Pension and other postretirement benefits
Total Other comprehensive income	$ 77	$ 96
Foreign currency translation
Other comprehensive income (loss)	336	(100)
Available-for-sale securities
Other comprehensive income		1
Cash flow hedges (N)
Total Other comprehensive income	34	115
Alcoa [Member]
Pension and other postretirement benefits
Balance at beginning of period	(3,532)	(4,063)
Unrecognized net actuarial loss and prior service cost/benefit	17	11
Tax expense	(3)	(3)
Total Other comprehensive income before reclassifications, net of tax	14	8
Amortization of net actuarial loss and prior service cost/benefit	98	132
Tax expense	(35)	(45)
Total amount reclassified from Accumulated other comprehensive loss, net of tax	63	87
Total Other comprehensive income	77	95
Balance at end of period	(3,455)	(3,968)
Foreign currency translation
Balance at beginning of period	179	1,147
Other comprehensive income (loss)	249	(116)
Balance at end of period	428	1,031
Available-for-sale securities
Balance at beginning of period	2	3
Other comprehensive income		1
Balance at end of period	2	4
Cash flow hedges (N)
Balance at beginning of period	(308)	(489)
Net change from periodic revaluations	36	136
Tax expense	(8)	(29)
Total Other comprehensive income before reclassifications, net of tax	28	107
Net amount reclassified to earnings	5	7
Tax expense	(1)	(1)
Total amount reclassified from Accumulated other comprehensive loss, net of tax	4	6
Total Other comprehensive income	32	113
Balance at end of period	(276)	(376)
Alcoa [Member] | Aluminum Contracts [Member]
Cash flow hedges (N)
Net amount reclassified to earnings	5	7
Noncontrolling Interests [Member]
Pension and other postretirement benefits
Balance at beginning of period	(51)	(77)
Amortization of net actuarial loss and prior service cost/benefit	1	1
Tax expense	(1)
Total amount reclassified from Accumulated other comprehensive loss, net of tax		1
Total Other comprehensive income		1
Balance at end of period	(51)	(76)
Foreign currency translation
Balance at beginning of period	(110)	257
Other comprehensive income (loss)	87	16
Balance at end of period	(23)	273
Cash flow hedges (N)
Balance at beginning of period	(2)	(5)
Net change from periodic revaluations	3	3
Tax expense	(1)	(1)
Total Other comprehensive income before reclassifications, net of tax	2	2
Total Other comprehensive income	2	2
Balance at end of period		$ (3)