Note 7 - Leases (Details Textual) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Jan. 01, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Lease, Liability, Total	$ 4,995
Cumulative Effect of New Accounting Principle in Period of Adoption			$ 238	$ 1,126
Operating Lease, Weighted Average Remaining Lease Term	13 years
Operating Lease, Weighted Average Discount Rate, Percent	12.60%
Operating Lease, Expense	$ 1,064
Accrued Liabilities, Current [Member]
Operating Lease, Liability, Current	1,452
Other Noncurrent Liabilities [Member]
Operating Lease, Liability, Noncurrent	3,543
Other Noncurrent Assets [Member]
Operating Lease, Right-of-Use Asset	$ 3,799
Minimum [Member]
Lessee, Operating Lease, Term of Contract	1 year
Maximum [Member]
Lessee, Operating Lease, Term of Contract	5 years
Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption			$ 238	$ 1,126
Accounting Standards Update 2016-02 [Member]
Operating Lease, Right-of-Use Asset		$ 3,621
Operating Lease, Liability, Total		4,822
Accounting Standards Update 2016-02 [Member] | Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption		$ 238