Product Warranty (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Product Warranty
Product warranty period	1 year
Changes in standard product warranty liability
Balance at the beginning of the period	$ 1,526	$ 1,428	$ 1,801
Warranties issued during the period	4,305	1,743	2,240
Settlements made during the period	(2,672)	(2,096)	(1,515)
Changes in estimate of liability for pre-existing warranties during the period	396	451	(1,098)
Balance at the end of the period	3,555	1,526	1,428
Product warranty classification
Amount classified as current				$ 3,363	$ 1,352	$ 1,316
Amount classified as long-term				192	174	112
Total warranty liability	$ 1,526	$ 1,428	$ 1,801	$ 3,555	$ 1,526	$ 1,428