Product Warranty (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Product Warranty
Product warranty period	1 year
Changes in standard product warranty liability
Balance at the beginning of the period	$ 1,526	$ 1,428
Warranties issued during the period	2,230	832
Settlements made during the period	(1,020)	(978)
Changes in estimate of liability for pre-existing warranties during the period	344	79
Balance at the end of the period	3,080	1,361
Product warranty classification
Amount classified as current			$ 2,886	$ 1,352	$ 1,326
Amount classified as long-term			194		35
Total warranty liability	$ 1,526	$ 1,428	$ 3,080	$ 1,526	$ 1,361