Note 5 - Revenue 1 (Details Textual) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Contract with Customer, Asset, after Allowance for Credit Loss, Current, Total	$ 0		$ 0		$ 181,000
Contract With Customer, Asset, Revenue Recognized	214,000		214,000		21,000
Contract with Customer, Liability, Total	0		0		0
Revenue, Remaining Performance Obligation, Amount	18,000		18,000		$ 211,000
Revenue from Contract with Customer, Including Assessed Tax	265,000	$ 454,000	3,690,000	$ 5,946,000
Income Tax Expense (Benefit), Total	26,000	31,000	$ 205,000	294,000
Foreign Tax Authority [Member] | National Tax Agency, Japan [Member]
Royalty Withholding Tax			5.00%
Income Tax Expense (Benefit), Total	13,000	17,000	$ 165,000	254,000
Royalty [Member]
Revenue from Contract with Customer, Including Assessed Tax		8,000	2,962,000	3,736,000
Royalty [Member] | GSK Research and License Agreement [Member]
Revenue from Contract with Customer, Including Assessed Tax		8,000	$ 193,000	772,000
Royalty Percentage			7.00%
Royalty [Member] | Daiichi Sankyo Collaberation and License Agreement [Member]
Revenue from Contract with Customer, Including Assessed Tax			$ 2,769,000	2,964,000
Royalty Percentage			4.00%		4.00%
Non-cash Royalty Revenue, Related to Sale of Future Royalties	$ 263,000	$ 352,000	$ 535,000	$ 2,116,000