Property and Equipment, Net (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Property and equipment	$ 61,534,000		$ 57,927,000
Less: accumulated depreciation and amortization	(37,365,000)		(34,852,000)
Property and equipment, net	24,169,000		23,075,000
Capital lease	3,100,000		3,100,000
Capital lease, accumulated depreciation	1,300,000		1,200,000
Depreciation and amortization expense	2,700,000	2,000,000
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment	30,107,000		27,464,000
Computer software
Property, Plant and Equipment [Line Items]
Property and equipment	9,310,000		9,277,000
Furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Property and equipment	2,110,000		2,031,000
Scanner appliances
Property, Plant and Equipment [Line Items]
Property and equipment	17,826,000		17,055,000
Scanner appliances and other computer equipment subject to subscription
Property, Plant and Equipment [Line Items]
Property and equipment, net	5,300,000		4,700,000
Scanner appliances and other computer equipment not placed in service
Property, Plant and Equipment [Line Items]
Property and equipment	1,000,000		600,000
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment	2,181,000		2,100,000
Other fixed assets not placed in service
Property, Plant and Equipment [Line Items]
Property and equipment	$ 1,700,000		$ 1,600,000