Derivatives and Fair Value Measurements - Location and Fair Value Amount of Derivative Instruments (Parenthetical) (Detail) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Derivative Liability Net of Cash Collateral [Member]
Derivatives Fair Value [Line Items]
Derivative liability balance	$ 12.6	$ 6.9
Derivatives Not Designated as Hedging Instruments under ASC 815 [Member] \| Metal Commodity Contracts [Member] \| Other Accrued Liabilities [Member] \| Derivative Counterparty [Member]
Derivatives Fair Value [Line Items]
Derivative liabilities, offsetting cash collateral	0.5	2.7
Derivative liability balance	$ 7.7	$ 6.7

Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=118260190&loc=d3e13433-108611

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant