Note 8 - Commitments and Contingencies (Details Textual)			1 Months Ended	12 Months Ended
	Dec. 01, 2017 USD ($)	May 25, 2017	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Apr. 01, 2019 USD ($)	Jan. 01, 2019 USD ($)
Operating Lease, Right-of-Use Asset				$ 4,856,000		$ 6,000,000
Other Nonoperating Income (Expense), Total				1,101,000	949,000
Lessee, Operating Lease, Term of Contract						5 years
Lessee, Operating Lease, Liability, Payments, Due, Total				5,711,000		$ 5,800,000
Lessee, Operating Lease, Discount Rate						6.50%
Operating Lease, Expense				1,400,000	2,000,000
Operating Lease, Right-of-Use Asset, Amortization				676,000
Prepaid Rent				461,000
Operating Lease, Liability, Total				4,857,000		$ 6,000,000
Class Action Lawsuits Related to IPO [Member] | Pending Litigation [Member]
Loss Contingency, New Claims Filed, Number		3
Loss Contingency Accrual, Payments			$ 1,760,000
Class Action Lawsuits Related to IPO [Member] | Settled Litigation [Member]
Litigation Settlement, Amount Awarded to Other Party from All Defendants					5,000,000
Other Income [Member]
Sublease Income				1,100,000
Accounting Standards Update 2016-02 [Member]
Operating Lease, Right-of-Use Asset							$ 1,800,000
Other Nonoperating Income (Expense), Total					$ 962,000
Operating Lease, Liability, Total							$ 1,800,000
Facility Lease [Member]
Incentive from Lessor				$ 369,000
Facility Sublease [Member]
Operating Leases Sublease Expiration Prior to Base Lease	15 days
Operating Leases, Monthly Minimum Sublease Rental Payments Receivable Final	$ 82,410