Income Taxes - Narrative (Details)	12 Months Ended
	Dec. 31, 2019 USD ($)
Operating loss carryforwards (NOLs)
Interest and/or penalties incurred	$ 0
Federal
Operating loss carryforwards (NOLs)
NOLs, subject to expiration	129,000,000
NOLs, not subject to expiration	30,300,000
California Franchise Tax Board
Operating loss carryforwards (NOLs)
NOLs	70,100,000
R&D credits | Federal
Operating loss carryforwards (NOLs)
Tax credits	2,400,000
R&D credits | California Franchise Tax Board
Operating loss carryforwards (NOLs)
Tax credits	$ 1,700,000