Property, Plant and Equipment - Additional Information (Detail) £ in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 GBP (£)	Dec. 31, 2020 USD ($)
Property Plant And Equipment [Line Items]
Finance lease assets gross value	$ 3,906		$ 3,906			$ 3,430
Finance lease, lease related accumulated amortization	1,164		1,164			$ 1,222
Amortization on assets under finance leases	124	$ 107	342	$ 245
Union Electric Steel UK Limited [Member]
Property Plant And Equipment [Line Items]
Land and buildings held as collateral	$ 2,856		$ 2,856		£ 2,122