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Exit Charges - Additional Information (Detail) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2025 USD ($)	Sep. 30, 2025 USD ($)	Sep. 30, 2025 USD ($) Employee	Jun. 30, 2025 USD ($)	Dec. 31, 2024 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring charges		$ 3,069	$ 9,819
Outstanding exit charges		5,969	5,969	$ 5,922	$ 0
Accumulated other comprehensive loss		(58,044)	(58,044)		$ (66,836)
Union Electric Steel UK Limited [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges		2,253	$ 9,003
Number of employees under existing benefit plans \| Employee			168
Carrying value of investment		23,000	$ 23,000
Estimated fair value of liabilities and assets		0	0
Accumulated other comprehensive loss		29,000	29,000
Alloys Unlimited and Processing, LLC.[Member]
Restructuring Cost and Reserve [Line Items]
Closure costs		800	$ 800
Number of employees under existing benefit plans \| Employee			15
Accrued Payrolls and Employee Benefits [Member]
Restructuring Cost and Reserve [Line Items]
Outstanding exit charges		5,121	$ 5,121
Other Noncurrent Liabilities [Member]
Restructuring Cost and Reserve [Line Items]
Outstanding exit charges		848	848
Minimum [Member] \| Revolving Credit Facility [Member] \| Union Electric Steel UK Limited [Member]
Restructuring Cost and Reserve [Line Items]
Amount of funds expected to be returned to the lenders		7,000	7,000
Minimum [Member] \| Forecast [Member] \| Union Electric Steel UK Limited [Member]
Restructuring Cost and Reserve [Line Items]
Non-cash impairment charge	$ 43,000
Maximum [Member] \| Revolving Credit Facility [Member] \| Union Electric Steel UK Limited [Member]
Restructuring Cost and Reserve [Line Items]
Amount of funds expected to be returned to the lenders		$ 9,000	$ 9,000
Maximum [Member] \| Forecast [Member] \| Union Electric Steel UK Limited [Member]
Restructuring Cost and Reserve [Line Items]
Non-cash impairment charge	$ 45,000