Balance Sheet Data - Warranty Accrual (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Movement in Standard Product Warranty Accrual [Roll Forward]
Beginning balance	$ 1,076	$ 1,178
Accrual for current period warranties	885	672
Warranty costs incurred	(938)	(774)
Ending balance	$ 1,023	$ 1,076