Note 15 - Unaudited Quarterly Results (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2018

Notes Tables

Quarterly Financial Information [Table Text Block]

	2018 Quarter Ended
	March 31			June 30			September 30			December 31
Revenues	$	3,189		$	3,878		$	5,317		$	3,238
Operating expenses	$	15,607		$	18,216		$	30,365		$	17,790
Operating loss	$	(12,418	)	$	(14,338	)	$	(25,048	)	$	(14,552	)
Net loss	$	(13,424	)	$	(15,172	)	$	(24,357	)	$	(14,704	)
Net loss per share - basic and diluted	$	(0.19	)	$	(0.20	)	$	(0.30	)	$	(0.17	)

	2017 Quarter Ended
	March 31			June 30			September 30			December 31
Revenues	$	2,347		$	2,765		$	2,697		$	3,889
Operating expenses	$	17,600		$	18,325		$	17,002		$	17,171
Operating loss	$	(15,253	)	$	(15,560	)	$	(14,305	)	$	(13,282	)
Net loss	$	(16,360	)	$	(16,636	)	$	(15,352	)	$	(2,665	)
Net loss per share - basic and diluted	$	(0.23	)	$	(0.24	)	$	(0.22	)	$	(0.04	)