Investments in Privately-Held Raw Material Companies - Minority Investment Entities (Details) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Jun. 30, 2021 USD ($) entity	Jun. 30, 2020 USD ($)
Summarized income information of all the minority investment entities that are not consolidated and accounted for under the equity method [Abstract]
Revenue	$ 33,735	$ 22,134		$ 65,085	$ 42,857
Gross Profit	12,238	6,768		23,774	12,290
Net income (loss)	4,615	959	$ 217	$ 8,380	1,176
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	10,264	3,605		$ 18,789	7,558
Gross Profit	5,537	958		9,344	2,026
Operating income	4,693	265		7,753	462
Net income (loss)	4,491	(160)		7,103	(158)
Minority investment entities
Entity portion of loss from unconsolidated equity method investments, including impairment charges	$ 1,500	$ (200)		$ 2,600	$ (300)