Income Taxes - Income Tax Expense (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current tax provision (benefit):
Federal	$ 0	$ 0	$ 0
State	106,000	81,000	68,000
Foreign	386,000	104,000	140,000
Deferred tax provision (benefit):
Federal	0	0	0
State	0	0	0
Foreign	0	0	0
Income Tax Expense (Benefit)	$ 492,000	$ 185,000	$ 208,000