Selected Quarterly Financial Data (Tables)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Financial Information [Table Text Block]

	Quarter Ended
	March 31, 2017		June 30, 2017		September 30, 2017		December 31, 2017*
Loss from operations	$	(8,149)	$	(6,475)	$	(5,842)	$	(5,783)
Net (loss) income	$	(3,058)	$	(4,315)	$	(10,930)	$	2,812
Net (loss) income per share – basic	$	(0.02)	$	(0.03)	$	(0.14)	$	0.02
Net (loss) income per share – dilutive	$	(0.02)	$	(0.03)	$	(0.14)	$	0.02
Weighted average common share – basic		117,447,260		123,005,220		128,279,674		128,566,883
Weighted average common share – dilutive		117,447,260		123,005,220		128,279,674		150,847,262

	Quarter Ended
	March 31, 2016		June 30, 2016		September 30, 2016		December 31, 2016
Loss from operations	$	(10,581)	$	(9,311)	$	(9,156)	$	(10,204)
Net (loss)	$	(11,078)	$	(5,764)	$	(8,489)	$	(2,472)
Net loss per share – basic	$	(0.12)	$	(0.06)	$	(0.09)	$	(0.02)
Net loss per share – dilutive	$	(0.12)	$	(0.10)	$	(0.09)	$	(0.02)
Weighted average common share – basic		90,826,752		91,015,733		91,441,687		103,804,308
Weighted average common share – dilutive		90,826,752		93,930,540		91,441,687		103,804,308