Derivatives and Fair Value Measurements - Volume of Company 's Activity in Derivative Instruments (Detail) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2020 USD ($) T	Dec. 31, 2019 USD ($) T bbl
Iron Ore Swap Contracts [Member]
Derivatives Fair Value [Line Items]
Derivative Instruments, Notional Value	240,000	420,000
Crude Oil Swap Contracts [Member]
Derivatives Fair Value [Line Items]
Derivative Instruments, Notional Value \| bbl		38,000
Aluminum Swap Contracts [Member]
Derivatives Fair Value [Line Items]
Derivative Instruments, Notional Value	14,915	23,949
Hot Roll Coil Swap Contracts [Member]
Derivatives Fair Value [Line Items]
Derivative Instruments, Notional Value	30,553	47,155
Nickel Swap Contracts [Member]
Derivatives Fair Value [Line Items]
Derivative Instruments, Notional Value	338	3,164
Foreign Exchange Contracts [Member]
Derivatives Fair Value [Line Items]
Derivative notional amount \| $	$ 2.8	$ 2.0
Interest Rate Swaps [Member]
Derivatives Fair Value [Line Items]
Derivative notional amount \| $	$ 160.0	$ 310.0

Nominal mass used to calculate payments on a derivative instrument.

No definition available.

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- Definition

Nominal volume used to calculate payments on a derivative instrument.

+ References

No definition available.

+ Details

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- Definition

Nominal or face amount used to calculate payment on derivative.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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