Warranty Accrual Activity (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Movement in Standard Product Warranty Accrual [Roll Forward]
Balance at beginning of period	$ 3,148	$ 3,104
Charged to cost of revenues	976	1,195
Actual warranty expenditures	(1,138)	$ (1,047)
Balance at end of period	$ 2,986