Note 1 - Significant Accounting Policies (Tables)

9 Months Ended

Sep. 30, 2019

Notes Tables

Debt Securities, Available-for-sale [Table Text Block]

	September 30, 2019
	Amortized Cost		Accrued Interest		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Obligations of the U.S. Government and its agencies	$	16,464	$	86	$	38	$	(2	)	$	16,586
Corporate debt securities		19,360		151		19		(5	)		19,525
Certificates of deposit		2,398		13		10		—			2,421
Total investments	$	38,222	$	250	$	67	$	(7	)	$	38,532

	December 31, 2018
	Amortized Cost		Accrued Interest		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Obligations of U.S. Government and its agencies	$	50,613	$	176	$	15	$	(131	)	$	50,673
Corporate debt securities		45,793		254		4		(171	)		45,880
Certificates of deposit		3,559		14		—		(14	)		3,559
Total investments	$	99,965	$	444	$	19	$	(316	)	$	100,112

Available For Sale Securities Debt Maturities Fair Value [Table Text Block]

	September 30, 2019		December 31, 2018
Maturing in one year or less	$	38,532	$	77,736
Maturing after one year through two years		—		22,376
Total investments	$	38,532	$	100,112

Schedule of Receivables from Collaborations [Table Text Block]

	September 30, 2019
	Billed		Unbilled		Total
U.S. Department of Health and Human Services	$	477	$	1,292	$	1,769
Shionogi & Co. Ltd.		160		—		160
Green Cross Corporation		303		27		330
Mundipharma International Holdings Limited		40		—		40
Seqirus UK Limited		947		352		1,299
Total receivables	$	1,927	$	1,671	$	3,598

	December 31, 2018
	Billed		Unbilled		Total
U.S. Department of Health and Human Services	$	—	$	1,525	$	1,525
Shionogi & Co. Ltd.		854		—		854
Green Cross Corporation		876		28		904
Mundipharma International Holdings Limited		44		—		44
Seqirus UK Limited		940		26		966
Total receivables	$	2,714	$	1,579	$	4,293

Disaggregation of Revenue [Table Text Block]

	Three Months				Nine Months
	2019		2018		2019		2018
Product sales	$	335	$	—	$	2,014	$	—
Royalty revenue		508		523		3,526		4,326
Collaborative and other research and development revenues:
U.S. Department of Health and Human Services		932		931		3,570		1,598
Seqirus UK Limited		—		—		—		12,000
Total collaborative and other research and development revenues		932		931		3,570		13,598
Total revenues	$	1,775	$	1,454	$	9,110	$	17,924