Income Taxes - Deferred (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Net operating loss carryforwards	$ 119,109,000	$ 112,553,000
Stock-based compensation	747,000	671,000
Property, plant and equipment	3,287,000	2,940,000
Other	3,364,000	2,985,000
Deferred tax assets, gross	126,507,000	119,149,000
Less: Valuation allowance	(125,528,000)	(118,283,000)
Total deferred tax assets	979,000	866,000
Deferred tax liabilities:
Property, plant and equipment	(778,000)	(686,000)
Other	(201,000)	(180,000)
Total deferred tax liabilities	(979,000)	(866,000)
Net deferred tax asset (liability)	$ 0	$ 0
Corporate tax rate	21.00%	21.00%
GILTI income	$ 2,600,000	$ 0