Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 3,508	$ 3,577	$ 4,605
Other comprehensive income (loss):
Tax (expense) benefit			(2)
Total Other comprehensive income, net of tax	22	80	16
Ending balance	3,601	3,508	3,577
Accumulated other comprehensive loss balance at end of period
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(1,863)	(1,943)	(3,329)
Other comprehensive income (loss):
Total Other comprehensive income, net of tax	22	80	16
Ending balance	(1,841)	(1,863)	(1,943)
Pension and other postretirement benefits (H)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(799)	(980)	(2,732)
Other comprehensive income (loss):
Unrecognized net actuarial gain (loss) and prior service cost/benefit	87	111	(211)
Tax (expense) benefit	(18)	(26)	48
Total Other comprehensive income (loss) before reclassifications, net of tax	69	85	(163)
Amortization of net actuarial loss and prior service cost	99	123	149
Tax (expense) benefit	(22)	(27)	(32)
Total amount reclassified from Accumulated other comprehensive income (loss), net of tax	77	96	117
Total Other comprehensive income, net of tax	146	181	(46)
Transfer to Arconic Corporation	0	0	1,798
Ending balance	(653)	(799)	(980)
Foreign currency translation
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(1,062)	(966)	(596)
Other comprehensive income (loss):
Total Other comprehensive income (loss) before reclassifications, net of tax	(131)	(96)	58
Transfer to Arconic Corporation	0	0	(428)
Ending balance	(1,193)	(1,062)	(966)
Cash flow hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(2)	3	(1)
Other comprehensive income (loss):
Unrecognized net actuarial gain (loss) and prior service cost/benefit	(8)	20	0
Tax (expense) benefit	2	(4)	0
Total Other comprehensive income (loss) before reclassifications, net of tax	(6)	16	0
Amortization of net actuarial loss and prior service cost	17	(26)	6
Tax (expense) benefit	(4)	5
Total amount reclassified from Accumulated other comprehensive income (loss), net of tax	13	(21)	4
Total Other comprehensive income, net of tax	7	(5)	4
Ending balance	$ 5	$ (2)	$ 3