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Derivative Financial Instruments and Hedging (Details2) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Cash Flow Hedging
Derivatives Fair Value [Line Items]
Derivative Instruments Gain Loss Reclassified From Accumulated OCI Into Income Effective Portion Net	$ (1.4)	$ 5.4	$ (0.1)	$ 24.7
Cash Flow Hedging \| Other Comprehensive Income (Loss) [Member]
Derivatives Fair Value [Line Items]
Net derivative gain (loss) on hedge transactions	(2.4)	5.8	(15.7)	36.8
Nickel and other raw material contracts \| Cash Flow Hedging
Derivatives Fair Value [Line Items]
Derivative Instruments Gain Loss Reclassified From Accumulated OCI Into Income Effective Portion Net	(0.4)	0.8	3.5	15.3
Nickel and other raw material contracts \| Cash Flow Hedging \| Other Comprehensive Income (Loss) [Member]
Derivatives Fair Value [Line Items]
Net derivative gain (loss) on hedge transactions	(1.6)	(0.7)	(8.5)	16.6
Interest Rate Swap \| Cash Flow Hedging
Derivatives Fair Value [Line Items]
Derivative Instruments Gain Loss Reclassified From Accumulated OCI Into Income Effective Portion Net	0.3	0.0	0.8	(0.3)
Interest Rate Swap \| Cash Flow Hedging \| Other Comprehensive Income (Loss) [Member]
Derivatives Fair Value [Line Items]
Net derivative gain (loss) on hedge transactions	0.1	0.6	0.3	2.1
Natural gas contracts \| Cash Flow Hedging
Derivatives Fair Value [Line Items]
Derivative Instruments Gain Loss Reclassified From Accumulated OCI Into Income Effective Portion Net	(1.4)	4.1	(4.6)	9.1
Natural gas contracts \| Cash Flow Hedging \| Other Comprehensive Income (Loss) [Member]
Derivatives Fair Value [Line Items]
Net derivative gain (loss) on hedge transactions	(1.0)	5.4	(7.8)	17.2
Foreign exchange contracts \| Cash Flow Hedging
Derivatives Fair Value [Line Items]
Derivative Instruments Gain Loss Reclassified From Accumulated OCI Into Income Effective Portion Net	0.1	0.5	0.2	0.6
Foreign exchange contracts \| Cash Flow Hedging \| Other Comprehensive Income (Loss) [Member]
Derivatives Fair Value [Line Items]
Net derivative gain (loss) on hedge transactions	0.1	$ 0.5	0.3	$ 0.9
Designated as Hedging Instrument
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Asset	4.2		4.2		$ 18.0
Derivative Fair Value Of Derivative Liability	9.3		9.3		4.6
Designated as Hedging Instrument \| Nickel and other raw material contracts \| Prepaid expenses and other current assets
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Asset	2.5		2.5		12.5
Designated as Hedging Instrument \| Nickel and other raw material contracts \| Other assets
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Asset	0.0		0.0		0.5
Designated as Hedging Instrument \| Nickel and other raw material contracts \| Accrued liabilities
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Liability	5.0		5.0		2.1
Designated as Hedging Instrument \| Nickel and other raw material contracts \| Other long-term liabilities
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Liability	0.5		0.5		0.0
Designated as Hedging Instrument \| Interest Rate Swap \| Prepaid expenses and other current assets
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Asset	1.2		1.2		1.4
Designated as Hedging Instrument \| Interest Rate Swap \| Other assets
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Asset	0.0		0.0		0.5
Designated as Hedging Instrument \| Natural gas contracts \| Prepaid expenses and other current assets
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Asset	0.1		0.1		2.4
Designated as Hedging Instrument \| Natural gas contracts \| Other assets
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Asset	0.2		0.2		0.7
Designated as Hedging Instrument \| Natural gas contracts \| Accrued liabilities
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Liability	3.3		3.3		2.0
Designated as Hedging Instrument \| Natural gas contracts \| Other long-term liabilities
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Liability	0.5		0.5		0.5
Designated as Hedging Instrument \| Foreign exchange contracts \| Prepaid expenses and other current assets
Derivatives Fair Value [Line Items]
Derivative Fair Value Of Derivative Asset	$ 0.2		$ 0.2		$ 0.0