Pension and Other Postretirement Benefits - Schedule of Obligations and Funded Status (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Amounts recognized in the Consolidated Balance Sheet consist of:
Current liabilities	$ (12)	$ (17)
Noncurrent liabilities	(153)	(198)
Pension benefits
Change in benefit obligation
Benefit obligation at beginning of year	2,713	7,249
Transfer to Arconic Corporation	0	(4,355)
Service cost	4	6
Interest cost	47	71
Amendments	3	6
Actuarial (gains) losses	55	(313)
Settlements	(275)	(398)
Benefits paid	(140)	(153)
Medicare Part D subsidy receipts	0	0
Foreign currency translation impact	1	26
Benefit obligation at end of year	2,296	2,713
Change in plan assets
Fair value of plan assets at beginning of year	1,724	4,868
Transfer to Arconic Corporation	0	(2,982)
Actual return on plan assets	124	203
Employer contributions	96	227
Benefits paid	(123)	(136)
Administrative expenses	(12)	(12)
Settlement payments	(277)	(413)
Foreign currency translation impact	(1)	(31)
Fair value of plan assets at end of year	1,531	1,724
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract]
Funded status	(765)	(989)
Amounts recognized in the Consolidated Balance Sheet consist of:
Noncurrent assets	22	12
Current liabilities	(16)	(16)
Noncurrent liabilities	(771)	(985)
Net amount recognized	(765)	(989)
Amounts recognized in Accumulated Other Comprehensive Loss consist of:
Net actuarial loss	1,067	1,274
Prior service cost (benefit)	3	6
Net amount recognized, before tax effect	1,070	1,280
Other changes in plan assets and benefit obligations recognized in Other Comprehensive Loss consist of:
Net actuarial (benefit) loss	(81)	166
Amortization of accumulated net actuarial (loss) gain	(125)	(123)
Loss transferred to Arconic Corporation	0	(2,144)
Prior service cost (benefit)	3	5
Amortization of prior service benefit	(7)	0
Prior service credit transferred to Arconic Corporation	0	0
Net amount recognized, before tax effect	(210)	(2,096)
Other postretirement benefits
Change in benefit obligation
Benefit obligation at beginning of year	215	786
Transfer to Arconic Corporation	0	(569)
Service cost	2	2
Interest cost	5	7
Amendments	(31)	(11)
Actuarial (gains) losses	10	(14)
Settlements	0	0
Benefits paid	(17)	(17)
Medicare Part D subsidy receipts	1	3
Foreign currency translation impact	0	0
Benefit obligation at end of year	165	215
Change in plan assets
Fair value of plan assets at beginning of year	0	0
Transfer to Arconic Corporation	0	0
Actual return on plan assets	0	0
Employer contributions	0	0
Benefits paid	0	0
Administrative expenses	0	0
Settlement payments	0	0
Foreign currency translation impact	0	0
Fair value of plan assets at end of year	0	0
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract]
Funded status	(165)	(215)
Amounts recognized in the Consolidated Balance Sheet consist of:
Noncurrent assets	0	0
Net amount recognized	(165)	(215)
Amounts recognized in Accumulated Other Comprehensive Loss consist of:
Net actuarial loss	11	22
Prior service cost (benefit)	(49)	(28)
Net amount recognized, before tax effect	(38)	(6)
Other changes in plan assets and benefit obligations recognized in Other Comprehensive Loss consist of:
Net actuarial (benefit) loss	(10)	14
Amortization of accumulated net actuarial (loss) gain	0	1
Loss transferred to Arconic Corporation	0	(170)
Prior service cost (benefit)	(31)	(11)
Amortization of prior service benefit	9	5
Prior service credit transferred to Arconic Corporation	0	13
Net amount recognized, before tax effect	(32)	(148)
United States | Pension benefits
Change in benefit obligation
Benefit obligation at beginning of year	2,327
Benefit obligation at end of year	2,039	2,327
Change in plan assets
Fair value of plan assets at beginning of year	1,361
Fair value of plan assets at end of year	1,278	1,361
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract]
Funded status	$ (761)	$ (966)