The Company and Summary of Significant Accounting Policies (Details) € in Millions, £ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 GBP (£) contract customer	Dec. 31, 2016 EUR (€) contract customer	Dec. 31, 2016 USD ($) contract customer	Dec. 31, 2015 GBP (£) customer	Dec. 31, 2015 EUR (€) customer	Dec. 31, 2015 USD ($) customer
Goodwill and Intangible Assets
Impairment of intangible assets	$ 0	$ 255,000	$ 0
Software Development Costs
Capitalized software development costs	0	99,000	98,000
Cost of intangible assets							$ 3,469,000			$ 3,469,000
Accumulated amortization of intangible assets							$ 2,522,000			2,149,000
Derivative Financial Instruments
Derivative, number of instruments held | contract					2	2	2
Derivative, notional amount								£ 2.6	€ 6.1
Foreign currency contract, asset, fair value disclosure							$ 0			0
Derivative instruments not designated as hedging instruments, gain	554,000	608,000	727,000
Foreign currency transaction loss, before tax	(1,324,000)	(1,051,000)	(1,391,000)
Total foreign exchange loss, net	(770,000)	(444,000)	(664,000)
Advertising Expenses
Advertising expense	7,700,000	6,100,000	5,300,000
Foreign exchange losses	$ 770,000	$ 444,000	$ 664,000
Income Taxes
Noncurrent deferred tax assets							16,590,000			16,079,000
Effect of early adoption of accounting guidance
Income Taxes
Noncurrent deferred tax assets										8,500,000
Minimum
Property Equipment, Net
Property, plant and equipment, useful life	3 years
Goodwill and Intangible Assets
Finite-lived intangible asset, useful life	3 years
Maximum
Property Equipment, Net
Property, plant and equipment, useful life	5 years
Goodwill and Intangible Assets
Finite-lived intangible asset, useful life	14 years
Scanner appliances
Property Equipment, Net
Property, plant and equipment, useful life	3 years
Forward contracts
Derivative Financial Instruments
Derivative, notional amount					£ 4.6	€ 7.6
Foreign currency contract, asset, fair value disclosure							0			0
Software and software development costs
Software Development Costs
Cost of intangible assets							400,000
Accumulated amortization of intangible assets							$ 300,000			$ 300,000
Customer concentration risk | Accounts receivable
Concentration of Credit Risk
Concentration risk, number of customers | customer					0	0	0	0	0	0
Scenario, Forecast [Member] | Accounting Standards Update 2016-09 [Member] | Retained Earnings [Member]
Income Taxes
Cumulative effect adjustment				$ (8,500,000)