Note 6 - Revenue 1 (Details Textual) - USD ($)	3 Months Ended								12 Months Ended		37 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Jun. 28, 2018	Sep. 30, 2015
Contract with Customer, Asset, Net, Current, Total	$ 181,000				$ 0				$ 181,000	$ 0
Contract With Customer, Asset, Revenue Recognized	21,000				0				21,000	0
Contract with Customer, Liability, Total	0								0
Revenue from Contract with Customer, Including Assessed Tax	3,916,000	$ 454,000	$ 85,000	$ 5,407,000	$ 1,767,000	$ 281,000	$ 608,000	$ 1,503,000	9,862,000	4,159,000
Income Tax Expense (Benefit), Total									$ 490,000	109,000
Foreign Tax Authority [Member] | National Tax Agency, Japan [Member]
Royalty Withholding Tax									5.00%
Income Tax Expense (Benefit), Total									$ 435,000	102,000
Government Contract [Member]
Contract Value											$ 15,700,000	$ 14,000,000
Contract Value, Adjustment											$ 1,700,000
Revenues, Total										1,344,000
Contract with Customer, Asset, Credit Loss Expense (Reversal)									20,000
Contract with Customer, Asset, Allowance for Credit Loss, Period Increase (Decrease), Total									(20,000)
Contract with Customer, Asset, Allowance for Credit Loss, Writeoff	$ 20,000
Revenue from Contract with Customer, Including Assessed Tax									(20,000)	1,344,000
Royalty [Member]
Revenue from Contract with Customer, Including Assessed Tax									4,446,000	1,340,000
Royalty [Member] | GSK Research and License Agreement [Member]
Revenue from Contract with Customer, Including Assessed Tax									$ 778,000	$ 788,000
Royalty Percentage									7.00%	7.00%
Royalty [Member] | Daiichi Sankyo Collaberation and License Agreement [Member]
Revenue from Contract with Customer, Including Assessed Tax									$ 3,668,000	$ 552,000
Royalty Percentage									4.00%
Non-cash Royalty Revenue, Related to Sale of Future Royalties									$ 5,030,000	$ 1,475,000