Note 6 - Revenue 1 (Details Textual) - USD ($)		3 Months Ended												12 Months Ended
	Jun. 28, 2018	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	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, 2020	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2015
Contract with Customer, Asset, after Allowance for Credit Loss, Current, Total		$ 0				$ 181,000								$ 0	$ 181,000
Contract With Customer, Asset, Revenue Recognized		219,000				21,000								219,000	21,000
Contract with Customer, Liability, Total		0				0								0	0
Revenue, Remaining Performance Obligation, Amount		13,000				211,000								13,000	211,000
Revenue from Contract with Customer, Including Assessed Tax		$ 356,000	$ 265,000	$ 523,000	$ 2,902,000	$ 3,916,000	$ 454,000	$ 85,000	$ 5,407,000	$ 1,767,000	$ 281,000	$ 608,000	$ 1,503,000	4,046,000	9,862,000	$ 4,159,000
Income Tax Expense (Benefit), Total														$ 238,000	490,000	109,000
Foreign Tax Authority [Member] | National Tax Agency, Japan [Member]
Royalty Withholding Tax														5.00%
Income Tax Expense (Benefit), Total														$ 183,000	435,000	102,000
Government Contract [Member]
Contract Value	$ 15,700,000																$ 14,000,000
Contract Value, Adjustment	$ 1,700,000
Revenue from Contract with Customer, Including Assessed Tax															(20,000)	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
Royalty [Member]
Revenue from Contract with Customer, Including Assessed Tax														2,962,000	4,446,000	1,340,000
Royalty [Member] | GSK Research and License Agreement [Member]
Revenue from Contract with Customer, Including Assessed Tax														$ 193,000	778,000	788,000
Royalty Percentage														7.00%
Royalty [Member] | Daiichi Sankyo Collaberation and License Agreement [Member]
Revenue from Contract with Customer, Including Assessed Tax														$ 2,769,000	3,668,000	552,000
Royalty Percentage														4.00%
Non Cash Royalty Revenue [Member]
Revenue from Contract with Customer, Including Assessed Tax														$ 886,000	5,030,000	1,475,000
Non Cash Royalty Revenue [Member] | Daiichi Sankyo Collaberation and License Agreement [Member]
Revenue from Contract with Customer, Including Assessed Tax														$ 886,000	$ 5,030,000	$ 1,475,000