Income Taxes Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred Tax Assets [Abstract]
Deferred Tax Assets, Operating Loss Carryforwards	$ 30,702	$ 21,550	$ 20,661
Deferred Tax Assets, Inventory	3,101	3,838	4,101
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Allowance for Doubtful Accounts	182	184	181
Deferred Tax Assets, Tax Basis Differences	(69)	44	133
Deferred Tax Assets, Tax Credit Carryforwards	17,654	16,127	16,050
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Warranty Reserves	231	211	290
Deferred Tax Assets, Deferred Income	3	411	328
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Accrued Liabilities	6,878	5,538	5,730
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost	6,340	6,515	6,440
Deferred Tax Assets, Gross	65,022	54,418	53,914
Deferred Tax Assets, Valuation Allowance	(62,739)	(52,380)	(51,558)
Deferred Tax Assets, Net of Valuation Allowance	2,283	2,038	2,356
Deferred Tax Liabilities, Other	(1,919)	(1,854)	(1,695)
Deferred Tax Liabilities, Net	1,919	1,854	1,695
Deferred Tax Assets, Net	364	$ 184	$ 661
Undistributed Earnings of Foreign Subsidiaries	$ 92,800