Derivative Financial Instruments - Summary of Mark-to-Market Gain (Losses) on Derivative Instruments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Fair value adjustments, net, pretax	$ 16,030	$ 3,638	$ (864)
Fair value adjustments, net	159	804	631
Provisional metal sales contracts
Derivative Instruments, Gain (Loss) [Line Items]
Provisional gain (loss) on derivatives and commodity contracts	337	111	631
Zinc options
Derivative Instruments, Gain (Loss) [Line Items]
Net derivative gain (loss)	0	753	0
Interest rate swap
Derivative Instruments, Gain (Loss) [Line Items]
Net derivative gain (loss)	(178)	$ (60)	0
Zinc Options
Derivative Instruments, Gain (Loss) [Line Items]
Net derivative gain (loss)	$ 0		$ 0