Other Financial Statement Data (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Product Liability Contingency [Line Items]
Depreciation expense	$ 1,300,000	$ 1,300,000	$ 1,200,000
Amortization expense, 2018	147,000
Amortization expense, 2019	114,000
Amortization expense, 2020	80,000
Amortization expense, 2021	20,000
Amortization expense, 2022	$ 9,000
Minimum [Member]
Product Liability Contingency [Line Items]
Warranty period (in years)	1 year
Maximum [Member]
Product Liability Contingency [Line Items]
Warranty period (in years)	3 years