Investments in Privately-Held Raw Material Companies - Minority Investment Entities (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2022 USD ($) entity	Mar. 31, 2021 USD ($)
Summarized income information of all the minority investment entities that are not consolidated and accounted for under the equity method [Abstract]
Revenue	$ 39,653	$ 31,350
Gross profit	13,308	11,536
Net income	$ 3,972	3,765
Minority investment entities
Impaired entities | entity	1
Five Minority Investments
Summarized income information of all the minority investment entities that are not consolidated and accounted for under the equity method [Abstract]
Revenue	$ 10,734	8,525
Gross profit	5,999	3,807
Operating income	4,149	3,061
Net income	3,698	2,612
Minority investment entities
Entity income (loss) excluding impairment	$ 1,100	$ 1,100