Unaudited Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 13,386	$ 13,548	$ 9,741	$ 8,491	$ 9,568	$ 12,596	$ 15,175	$ 17,822	$ 45,166	$ 55,161	$ 73,664
Cost of sales	7,761	8,498	6,116	4,769	7,717	7,281	9,595	11,774	27,144	36,367	45,107
Net (loss)	$ (1,206)	$ (417)	$ (6,854)	$ (2,506)	$ (9,104)	$ (3,019)	$ (2,628)	$ (2,637)	$ (10,983)	$ (17,388)	$ (12,380)
Basic (in dollars per share)	$ 0.02	$ (0.01)	$ (0.24)	$ (0.07)	$ (0.03)	$ (0.03)	$ (0.03)	$ (0.03)	$ (0.46)	$ (0.74)	$ (0.54)
Diluted (in dollars per share)	$ (0.07)	$ (0.01)	$ (0.05)	$ (0.03)	$ (0.39)	$ (0.13)	$ (0.11)	$ (0.11)	$ (0.46)	$ (0.74)	$ (0.54)