Property, Plant and Equipment - Additional Information (Detail) £ in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 GBP (£)	Dec. 31, 2020 USD ($)
Property Plant And Equipment [Line Items]
Finance lease assets gross value	$ 2,981		$ 2,981			$ 3,430
Finance lease, lease related accumulated amortization	1,093		1,093			$ 1,222
Amortization on assets under finance leases	100	$ 68	218	$ 138
Union Electric Steel UK Limited [Member]
Property Plant And Equipment [Line Items]
Land and buildings held as collateral	$ 2,936		$ 2,936		£ 2,122