Segment Reporting - Summary of Concentration Risk (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Concentration Risk [Line Items]
Revenue	$ 832,828	$ 785,461	$ 711,502
Customer Concentration Risk [Member] | Asahi Formerly Johnson Matthey [Member]
Concentration Risk [Line Items]
Revenue	323,800	272,100	341,000
Customer Concentration Risk [Member] | Techemet Metal Trading [Member]
Concentration Risk [Line Items]
Revenue	62,200	81,800	9,400
Customer Concentration Risk [Member] | Ocean Partners [Member]
Concentration Risk [Line Items]
Revenue	176,400	161,000	149,700
Customer Concentration Risk [Member] | Toronto Dominion Bank
Concentration Risk [Line Items]
Revenue	61,900	88,600	35,100
Customer Concentration Risk [Member] | Argor-Heraeus
Concentration Risk [Line Items]
Revenue	$ 23,300	$ 79,900	$ 23,100
Product Concentration Risk [Member] | Dore [Member] | Revenue, Product and Service Benchmark
Concentration Risk [Line Items]
Concentration Risk, Percentage	74.00%	72.00%	68.00%
Product Concentration Risk [Member] | Concentrate [Member] | Revenue, Product and Service Benchmark
Concentration Risk [Line Items]
Concentration Risk, Percentage	26.00%	28.00%	32.00%