Fair Value Measurements - Summary of Gain (Loss) Derivative Instruments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value adjustments, net	$ 7,601	$ 16,030	$ 3,638
Equity Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized Gain (Loss) on Securities	(11,539)	15,348	(5,019)
Fair value adjustments, net	7,601	16,208	2,945
Realized gain (loss) on equity securities	19,140	860	7,964
Zinc Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net derivative gain (loss)	0	0	753
Interest rate swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value adjustments, net	$ 0	$ (178)	$ (60)