Derivatives and Fair Value Measurements - Location and Fair Value Amount of Derivative Instruments (Detail) - USD ($) $ in Millions	Mar. 31, 2020		Dec. 31, 2019
Derivatives Fair Value [Line Items]
Asset Derivatives, Fair Value	$ 1.2		$ 5.1
Liability Derivatives, Fair Value	13.1	[1]	9.6	[2]
Derivatives Not Designated as Hedging Instruments under ASC 815 [Member] | Metal Commodity Contracts [Member] | Prepaid Expenses and Other Current Assets [Member]
Derivatives Fair Value [Line Items]
Asset Derivatives, Fair Value	1.0		5.0
Derivatives Not Designated as Hedging Instruments under ASC 815 [Member] | Metal Commodity Contracts [Member] | Other Accrued Liabilities [Member]
Derivatives Fair Value [Line Items]
Liability Derivatives, Fair Value	8.2	[1]	9.4	[2]
Derivatives Not Designated as Hedging Instruments under ASC 815 [Member] | Crude Oil Contracts [Member] | Prepaid Expenses and Other Current Assets [Member]
Derivatives Fair Value [Line Items]
Asset Derivatives, Fair Value			0.1
Derivatives Not Designated as Hedging Instruments under ASC 815 [Member] | Foreign Exchange Contracts [Member] | Prepaid Expenses and Other Current Assets [Member]
Derivatives Fair Value [Line Items]
Asset Derivatives, Fair Value	0.2
Derivatives designated as hedging instruments under ASC 815 [Member] | Interest Rate Swap [Member] | Other Noncurrent Liabilities [Member]
Derivatives Fair Value [Line Items]
Liability Derivatives, Fair Value	$ 4.9		$ 0.2

[1] The offsetting cash collateral balance of $0.5 million held by the derivative counterparty brings the net metal commodity contract liability to $7.7 million and the net total derivative liability balance to $12.6 million as of March 31, 2020.

[2] The offsetting cash collateral balance of $2.7 million held by the derivative counterparty brought the net metal commodity contract liability to $6.7 million and the net total derivative liability balance to $6.9 million as of December 31, 2019.