Statement of Consolidated Comprehensive Income (Loss) (unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Net income	$ 119	$ 186	$ 653	$ 375
Other comprehensive income (loss), net of tax (C):
Change in unrecognized net actuarial loss and prior service cost/benefit related to pension and other postretirement benefits	31	(463)	110	(363)
Foreign currency translation adjustments	85	202	251	689
Net change in unrealized gains/losses on available-for-sale securities	1		(133)	4
Net change in unrecognized gains/losses on cash flow hedges	10	(348)	13	(567)
Total Other comprehensive income (loss), net of tax	127	(609)	241	(237)
Comprehensive income (loss)	246	(423)	894	138
Arconic [Member]
Net income	119	166	653	317
Other comprehensive income (loss), net of tax (C):
Change in unrecognized net actuarial loss and prior service cost/benefit related to pension and other postretirement benefits	31	(462)	110	(365)
Foreign currency translation adjustments	85	157	251	505
Net change in unrealized gains/losses on available-for-sale securities	1		(133)	4
Net change in unrecognized gains/losses on cash flow hedges	10	(338)	13	(571)
Total Other comprehensive income (loss), net of tax	127	(643)	241	(427)
Comprehensive income (loss)	$ 246	(477)	$ 894	(110)
Noncontrolling Interests [Member]
Net income		20		58
Other comprehensive income (loss), net of tax (C):
Change in unrecognized net actuarial loss and prior service cost/benefit related to pension and other postretirement benefits		(1)		2
Foreign currency translation adjustments		45		184
Net change in unrecognized gains/losses on cash flow hedges		(10)		4
Total Other comprehensive income (loss), net of tax		34		190
Comprehensive income (loss)		$ 54		$ 248