Investments in Privately-Held Raw Material Companies - Minority Investment Entities (Details) - Five Minority Investments - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Summarized income information of all the minority investment entities that are not consolidated and accounted for under the equity method [Abstract]
Net revenue	$ 5,052,000	$ 3,713,000	$ 12,610,000	$ 14,713,000
Gross profit (loss)	918,000	309,000	2,944,000	1,423,000
Operating (loss)	136,000	(436,000)	598,000	(1,857,000)
Net income (loss)	7,000	(502,000)	(151,000)	(2,518,000)
Minority investment entities
Entity portion of loss from unconsolidated equity method investments, including impairment charges	$ 45,000	$ 200,000	$ 200,000	$ 1,700,000