Note 1 - Significant Accounting Policies (Tables)

9 Months Ended

Sep. 30, 2017

Notes Tables

Available-for-sale Securities [Table Text Block]

	September 30, 2017
	Amortized Cost		Accrued Interest		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Obligations of the U.S. Government and its agencies	$	27,897	$	96	$	—	$	(7	)	$	27,986
Corporate debt securities		8,230		39		—		(8	)		8,261
Certificates of deposit		12,108		34		4		(6	)		12,140
Total investments	$	48,235	$	169	$	4	$	(21	)	$	48,387

	December 31, 2016
	Amortized Cost		Accrued Interest		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Obligations of the U.S. Government and its agencies	$	20,266	$	34	$	2	$	(4	)	$	20,298
Corporate debt securities		6,179		26		2		(8	)		6,199
Certificates of deposit		14,962		17		7		(11	)		14,975
Total investments	$	41,407	$	77	$	11	$	(23	)	$	41,472

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

	2017		2016
Maturing in one year or less	$	43,848	$	32,546
Maturing after one year through two years		4,539		8,926
Total investments	$	48,387	$	41,472

Schedule of Receivables from Collaborations [Table Text Block]

	September 30, 2017
	Billed		Unbilled		Total
U.S. Department of Health and Human Services	$	63	$	1,906	$	1,969
Shionogi & Co. Ltd.		653		—		653
Green Cross Corporation		48		—		48
Mundipharma International Holdings Limited		46		—		46
Seqirus UK Limited		5,794		475		6,269
Total receivables	$	6,604	$	2,381	$	8,985

	December 31, 2016
	Billed		Unbilled		Total
U.S. Department of Health and Human Services	$	—	$	3,495	$	3,495
Shionogi & Co. Ltd.		3,451		—		3,451
Green Cross Corporation		686		—		686
Seqirus UK Limited		957		179		1,136
Total receivables	$	5,094	$	3,674	$	8,768

Schedule of Revenues from Collaborations [Table Text Block]

	Three Months				Nine Months
	2017		2016		2017		2016
Product sales	$	1,501	$	—	$	1,501	$	—
Royalty revenue		442		3,501		7,252		6,020
Collaborative and other research and development revenues:
U.S. Department of Health and Human Services		1,490		3,813		4,305		9,846
Shionogi & Co. Ltd.		296		296		888		888
Seqirus UK Limited		5,031		153		7,350		616
Total collaborative and other research and development revenues		6,817		4,262		12,543		11,350
Total revenues	$	8,760	$	7,763	$	21,296	$	17,370