Product Warranty (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015
Product Warranty
Product warranty period	1 year
Changes in standard product warranty liability
Balance at the beginning of the period	$ 3,555	$ 1,526
Warranties issued during the period	2,286	3,543
Settlements made during the period	(3,570)	(1,611)
Changes in estimate of liability for pre-existing warranties during the period	551	345
Balance at the end of the period	2,822	3,803
Product warranty classification
Amount classified as current			$ 2,597	$ 3,363	$ 3,532
Amount classified as long-term			225		271
Total warranty liability	$ 3,555	$ 1,526	$ 2,822	$ 3,555	$ 3,803