Product Warranty (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Product Warranty
Product warranty period	1 year
Changes in standard product warranty liability
Balance at the beginning of the period	$ 3,555	$ 1,526	$ 1,428
Warranties issued during the period	3,125	4,305	1,743
Settlements made during the period	(4,249)	(2,672)	(2,096)
Changes in estimate of liability for pre-existing warranties during the period	235	396	451
Balance at the end of the period	2,666	3,555	1,526
Product warranty classification
Amount classified as current				$ 2,426	$ 3,363	$ 1,352
Amount classified as long-term				240	192	174
Total warranty liability	$ 3,555	$ 1,526	$ 1,428	$ 2,666	$ 3,555	$ 1,526