Product Warranty (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Dec. 31, 2015	Jun. 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	1,551	2,230
Settlements made during the period	(2,399)	(1,020)
Changes in estimate of liability for pre-existing warranties during the period	520	344
Balance at the end of the period	3,227	3,080
Product warranty classification
Amount classified as current			$ 2,958	$ 3,363	$ 2,886
Amount classified as long-term			269		194
Total warranty liability	$ 3,555	$ 1,526	$ 3,227	$ 3,555	$ 3,080