Property, Plant and Equipment - Additional Information (Detail) £ in Thousands	1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
	Jun. 30, 2023 USD ($)	Aug. 31, 2022 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2021 USD ($)	Sep. 30, 2024 GBP (£)
Property Plant And Equipment [Line Items]
Finance lease assets gross value			$ 3,539,000		$ 3,539,000		$ 4,223,000
Finance lease, lease related accumulated amortization			1,876,000		1,876,000		$ 1,959,000
Depreciation expense			$ 4,497,000	$ 4,295,000	$ 13,692,000	$ 12,844,000
Remaining lease term							20 years
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]			Long-Term Debt and Lease Obligation, Current		Long-Term Debt and Lease Obligation, Current		Long-Term Debt and Lease Obligation, Current		Long-Term Debt and Lease Obligation, Current
Estimated cost on upgrading existing equipment								$ 26,000,000
Interest capitalized on strategic capital projects			$ 0	425,000	$ 251,000	1,027,000
Depreciation on assets under finance leases			80,000	$ 115,000	242,000	$ 252,000
Capital Expenditures [Member]
Property Plant And Equipment [Line Items]
Proceeds from disbursement agreement	$ 2,500,000						$ 2,500,000
Estimated cost on upgrading existing equipment		$ 2,500,000
Union Electric Steel UK Limited [Member]
Property Plant And Equipment [Line Items]
Land and buildings held as collateral			$ 2,841,000		2,841,000				£ 2,122
UES Domestic [Member] | Construction-in-Process, Machinery and Equipment or Buildings [Member]
Property Plant And Equipment [Line Items]
Machinery and equipment purchased					$ 24,239,000