Derivative Financial Instruments - Summary of Mark-to-Market Gain (Losses) on Derivative Instruments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Fair value adjustments, net, pretax	$ 7,601	$ 16,030	$ 3,638
Fair value adjustments, net	959	159	804
Provisional metal sales contracts
Derivative Instruments, Gain (Loss) [Line Items]
Provisional gain (loss) on derivatives and commodity contracts	959	337	111
Interest rate swap
Derivative Instruments, Gain (Loss) [Line Items]
Net derivative gain (loss)	0	(178)	(60)
Zinc Options
Derivative Instruments, Gain (Loss) [Line Items]
Net derivative gain (loss)	$ 0	$ 0	$ 753