Statement Of Consolidated Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Net income	$ 99	$ 366
Other comprehensive income, net of tax:
Change in unrecognized net actuarial loss and prior service cost/benefit related to pension and other postretirement benefits	58	38
Foreign currency translation adjustments	309	442
Unrealized gains on available-for-sale securities:
Unrealized holding gains	2
Net amount reclassified to earnings
Net change in unrealized gains on available-for-sale securities	2
Unrecognized losses on derivatives (L):
Net change from periodic revaluations	(84)	(188)
Net amount reclassified to earnings	1	40
Net change in unrecognized losses on derivatives	(83)	(148)
Total Other comprehensive income, net of tax	286	332
Comprehensive income	385	698
Alcoa [Member]
Net income	94	308
Other comprehensive income, net of tax:
Change in unrecognized net actuarial loss and prior service cost/benefit related to pension and other postretirement benefits	56	37
Foreign currency translation adjustments	244	368
Unrealized gains on available-for-sale securities:
Unrealized holding gains	2
Net amount reclassified to earnings
Net change in unrealized gains on available-for-sale securities	2
Unrecognized losses on derivatives (L):
Net change from periodic revaluations	(82)	(188)
Net amount reclassified to earnings	1	40
Net change in unrecognized losses on derivatives	(81)	(148)
Total Other comprehensive income, net of tax	221	257
Comprehensive income	315	565
Non-Controlling Interests [Member]
Net income	5	58
Other comprehensive income, net of tax:
Change in unrecognized net actuarial loss and prior service cost/benefit related to pension and other postretirement benefits	2	1
Foreign currency translation adjustments	65	74
Unrealized gains on available-for-sale securities:
Unrealized holding gains
Net amount reclassified to earnings
Net change in unrealized gains on available-for-sale securities
Unrecognized losses on derivatives (L):
Net change from periodic revaluations	(2)
Net amount reclassified to earnings
Net change in unrecognized losses on derivatives	(2)
Total Other comprehensive income, net of tax	65	75
Comprehensive income	$ 70	$ 133