Quarterly Financial Summary (unaudited) (Tables)

12 Months Ended

Dec. 31, 2016

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Financial

	Quarters Ended
(in thousands, except per share data)	December 31, 2016			September 30, 2016			June 30, 2016			March 31, 2016
Product sales	$	715		$	1,180		$	1,037		$	1,053
Gross profit (loss)	$	(2,593	)	$	(1,435	)	$	(2,204	)	$	141
Operating loss	$	(10,383	)	$	(8,499	)	$	(8,507	)	$	(5,821	)
Net loss	$	(10,370	)	$	(8,489	)	$	(8,504	)	$	(5,816	)
Net loss per share – basic and diluted	$	(0.24	)	$	(0.20	)	$	(0.23	)	$	(0.16	)

	Quarters Ended
	December 31, 2015			September 30, 2015			June 30, 2015			March 31, 2015
Product sales	$	2,362		$	2,227		$	2,661		$	1,700
Gross profit (loss)	$	691		$	1,470		$	1,092		$	404
Operating loss	$	(5,477	)	$	(4,662	)	$	(4,947	)	$	(4,961	)
Net loss	$	(5,474	)	$	(4,666	)	$	(4,922	)	$	(4,956	)
Net loss per share – basic and diluted	$	(0.15	)	$	(0.13	)	$	(0.14	)	$	(0.14	)