Note 1 - Significant Accounting Policies and Concentrations of Risk (Tables)

12 Months Ended

Dec. 31, 2016

Notes Tables

Available-for-sale Securities [Table Text Block]

	December 31, 2016
	Amortized Cost		Accrued Interest		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Obligations of 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

	December 31, 2015
	Amortized Cost		Accrued Interest		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Obligations of U.S. Government and its agencies	$	26,557	$	88	$	—	$	(99	)	$	26,546
Corporate debt securities		21,820		184		—		(41	)		21,963
Certificates of deposit		21,884		20		6		(72	)		21,838
Total investments	$	70,261	$	292	$	6	$	(212	)	$	70,347

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

	2016		2015
Maturing in one year or less	$	32,546	$	22,664
Maturing after one year through two years		8,926		28,395
Maturing after two years		—		19,288
Total investments	$	41,472	$	70,347

Schedule of Receivables from Collaborations [Table Text Block]

	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

	December 31, 2015
	Billed		Unbilled		Total
U.S. Department of Health and Human Services	$	—	$	5,536	$	5,536
Shionogi & Co. Ltd.		469		—		469
Seqirus UK Limited		210		28		238
Total receivables	$	679	$	5,564	$	6,243

Schedule of Inventory, Current [Table Text Block]

	As of December 31,
	2016		2015
Work in process	$	500	$	1,612
Net inventories	$	500	$	1,612

Schedule of Accrued Liabilities [Table Text Block]

	December 31,
	2016		2015
Compensation and benefits	$	425	$	424
Development costs		7,427		10,398
Inventory		705		549
Professional fees		242		242
Duties and taxes		56		102
Other		1,981		4,522
Total accrued expenses	$	10,836	$	16,237

Schedule of Revenues from Collaborations [Table Text Block]

	2016		2015		2014
Product sales, net	$	2,269	$	6,291	$	33
Royalty revenue		9,682		2,386		3,025
Collaborative and other research and development revenues:
U.S. Department of Health and Human Services		12,449		16,337		9,366
Green Cross Corporation		—		132		—
Shionogi & Co. Ltd.		1,184		1,184		1,184
Seqirus UK Limited		769		21,927		—
Total collaborative and other research and development revenues		14,402		39,580		10,550
Total revenues	$	26,353	$	48,257	$	13,608