Statement Of Consolidated Comprehensive (Loss) Income (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Net income (loss)	$ 805	$ 392	$ (1,090)
Other comprehensive (loss) income, net of tax:
Change in unrecognized net actuarial loss and prior service cost/benefit related to pension and other postretirement benefits (W)	(652)	(144)	(102)
Foreign currency translation adjustments (A)	(708)	775	1,697
Unrealized gains on available-for-sale securities (I):
Unrealized holding (losses) gains		(5)	49
Net amount reclassified to earnings		4	381
Net change in unrealized gains on available-for-sale securities		(1)	430
Unrecognized losses on derivatives (X):
Net change from periodic revaluations	57	(17)	(614)
Net amount reclassified to earnings	122	138	(11)
Net change in unrecognized losses on derivatives	179	121	(625)
Total Other comprehensive (loss) income, net of tax	(1,181)	751	1,400
Comprehensive (loss) income	(376)	1,143	310
Alcoa, Inc. [Member]
Net income (loss)	611	254	(1,151)
Other comprehensive (loss) income, net of tax:
Change in unrecognized net actuarial loss and prior service cost/benefit related to pension and other postretirement benefits (W)	(593)	(140)	(110)
Foreign currency translation adjustments (A)	(543)	441	1,377
Unrealized gains on available-for-sale securities (I):
Unrealized holding (losses) gains		(5)	49
Net amount reclassified to earnings		4	381
Net change in unrealized gains on available-for-sale securities		(1)	430
Unrecognized losses on derivatives (X):
Net change from periodic revaluations	63	(21)	(609)
Net amount reclassified to earnings	121	138	(11)
Net change in unrecognized losses on derivatives	184	117	(620)
Total Other comprehensive (loss) income, net of tax	(952)	417	1,077
Comprehensive (loss) income	(341)	671	(74)
Noncontrolling Interests [Member]
Net income (loss)	194	138	61
Other comprehensive (loss) income, net of tax:
Change in unrecognized net actuarial loss and prior service cost/benefit related to pension and other postretirement benefits (W)	(59)	(4)	8
Foreign currency translation adjustments (A)	(165)	334	320
Unrecognized losses on derivatives (X):
Net change from periodic revaluations	(6)	4	(5)
Net amount reclassified to earnings	1
Net change in unrecognized losses on derivatives	(5)	4	(5)
Total Other comprehensive (loss) income, net of tax	(229)	334	323
Comprehensive (loss) income	$ (35)	$ 472	$ 384