Accrued Warranty (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Accrued Warranty
Balance at beginning of period	$ 228	$ 373
Accrued warranty expense	61	125
Warranty claims paid	(47)	(155)
Balance at end of period	$ 242	$ 343