This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 23
-URI http://asc.fasb.org/extlink&oid=123586518&loc=d3e1043-128460

Name:	us-gaap_BusinessCombinationAcquisitionRelatedCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Business Combinations, Goodwill and Intangible Assets - Additional Information (Details) - Alcoa Warrick LLC [Member] - USD ($) $ in Millions			3 Months Ended	9 Months Ended
	Sep. 30, 2021	Mar. 31, 2021	Sep. 30, 2021	Sep. 30, 2021
Finite Lived Intangible Assets [Line Items]
Business combination, purchase price	$ 670.0	$ 670.0
Selling, General, Administrative, Research and Development
Finite Lived Intangible Assets [Line Items]
Acquisition costs			$ 1.0	$ 15.0