Accrued Warranty - Summary of Activity (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Accrued Warranty
Balance at beginning of period	$ 338	$ 228
Accrued warranty expense	5	61
Warranty claims paid	(18)	(47)
Balance at end of period	$ 325	$ 242
Minimum
Accrued Warranty
Warrants period	1 year
Maximum
Accrued Warranty
Warrants period	5 years