Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016 USD ($) Country	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Schedule Of Accounting Policies [Line Items]
Number of Countries in which Entity Operates | Country	15
Gain (loss) from foreign currency transactions	$ 111,000	$ (1,247,000)	$ (1,382,000)
Cash equivalents maturity, Term	Cash equivalents are high-quality short term money market instruments and commercial paper with maturities at acquisition of three months or less.
Depreciation expense	$ 1,928,000	1,345,000	1,928,000
Investments	4,073,000	0
Software development costs were capitalized	0	0	0
Goodwill impairment	0	0	0
Changes in cash flow from financing activities	0	$ 318,000	$ 253,000
Change in Accounting Method Accounted for as Change in Estimate [Member]
Schedule Of Accounting Policies [Line Items]
Increase in provision for income taxes	169,000
Changes in cash flow from operating activities	(169,000)
Changes in cash flow from financing activities	$ 169,000
DigiNotar B.V. [Member]
Schedule Of Accounting Policies [Line Items]
Percentage of stock acquired by the Company	100.00%
Patents [Member]
Schedule Of Accounting Policies [Line Items]
Estimated useful lives of assets	20 years
Minimum [Member]
Schedule Of Accounting Policies [Line Items]
Estimated useful lives of assets	3 years
Warranty for hardware purchase	1 year
Extended product warranty period	1 year
Minimum [Member] | Software Development Costs [Member]
Schedule Of Accounting Policies [Line Items]
Estimated economic life of product	2 years
Minimum [Member] | Proprietary Technology [Member]
Schedule Of Accounting Policies [Line Items]
Estimated useful lives of assets	3 years
Minimum [Member] | Customer Relationships [Member]
Schedule Of Accounting Policies [Line Items]
Estimated useful lives of assets	5 years
Maximum [Member]
Schedule Of Accounting Policies [Line Items]
Estimated useful lives of assets	7 years
Warranty for hardware purchase	2 years
Extended product warranty period	4 years
Maximum [Member] | Software Development Costs [Member]
Schedule Of Accounting Policies [Line Items]
Estimated economic life of product	5 years
Maximum [Member] | Proprietary Technology [Member]
Schedule Of Accounting Policies [Line Items]
Estimated useful lives of assets	7 years
Maximum [Member] | Customer Relationships [Member]
Schedule Of Accounting Policies [Line Items]
Estimated useful lives of assets	12 years