Product Warranty (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Dec. 31, 2014	Sep. 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	3,543	1,028
Settlements made during the period	(1,611)	(1,511)
Changes in estimate of liability for pre-existing warranties during the period	345	264
Balance at the end of the period	3,803	1,209
Product warranty classification
Amount classified as current			$ 3,532	$ 1,352	$ 1,160
Amount classified as long-term			271		49
Total warranty liability	$ 1,526	$ 1,428	$ 3,803	$ 1,526	$ 1,209