Statement of Consolidated Comprehensive (Loss) Income (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Net income (loss)	$ 162	$ 805	$ 392
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)	(507)	(652)	(144)
Foreign currency translation adjustments (A)	(296)	(708)	775
Unrealized gains on available-for-sale securities (I):
Unrealized holding gains (losses)	2		(5)
Net amount reclassified to earnings			4
Net change in unrealized gains on available-for-sale securities	2		(1)
Unrecognized losses on derivatives (X):
Net change from periodic revaluations	(13)	57	(17)
Net amount reclassified to earnings	(34)	122	138
Net change in unrecognized losses on derivatives	(47)	179	121
Total Other comprehensive (loss) income, net of tax	(848)	(1,181)	751
Comprehensive (loss) income	(686)	(376)	1,143
Alcoa [Member]
Net income (loss)	191	611	254
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)	(529)	(593)	(140)
Foreign currency translation adjustments (A)	(202)	(543)	441
Unrealized gains on available-for-sale securities (I):
Unrealized holding gains (losses)	2		(5)
Net amount reclassified to earnings			4
Net change in unrealized gains on available-for-sale securities	2		(1)
Unrecognized losses on derivatives (X):
Net change from periodic revaluations	(12)	63	(21)
Net amount reclassified to earnings	(34)	121	138
Net change in unrecognized losses on derivatives	(46)	184	117
Total Other comprehensive (loss) income, net of tax	(775)	(952)	417
Comprehensive (loss) income	(584)	(341)	671
Noncontrolling Interests [Member]
Net income (loss)	(29)	194	138
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)	22	(59)	(4)
Foreign currency translation adjustments (A)	(94)	(165)	334
Unrecognized losses on derivatives (X):
Net change from periodic revaluations	(1)	(6)	4
Net amount reclassified to earnings		1
Net change in unrecognized losses on derivatives	(1)	(5)	4
Total Other comprehensive (loss) income, net of tax	(73)	(229)	334
Comprehensive (loss) income	$ (102)	$ (35)	$ 472