Property and Equipment, Net (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Property and equipment	$ 63,976,000		$ 63,976,000		$ 57,927,000
Less: accumulated depreciation and amortization	(39,964,000)		(39,964,000)		(34,852,000)
Property and equipment, net	24,012,000		24,012,000		23,075,000
Capital lease	3,100,000		3,100,000		3,100,000
Capital lease, accumulated depreciation	1,400,000		1,400,000		1,200,000
Depreciation and amortization expense	2,900,000	2,300,000	5,600,000	4,300,000
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment	31,689,000		31,689,000		27,464,000
Computer software
Property, Plant and Equipment [Line Items]
Property and equipment	9,313,000		9,313,000		9,277,000
Furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Property and equipment	2,416,000		2,416,000		2,031,000
Scanner appliances
Property, Plant and Equipment [Line Items]
Property and equipment	18,323,000		18,323,000		17,055,000
Scanner appliances and other computer equipment subject to subscription
Property, Plant and Equipment [Line Items]
Property and equipment, net	5,600,000		5,600,000		4,700,000
Scanner appliances and other computer equipment not placed in service
Property, Plant and Equipment [Line Items]
Property and equipment	900,000		900,000		600,000
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment	2,235,000		2,235,000		2,100,000
Other fixed assets not placed in service
Property, Plant and Equipment [Line Items]
Property and equipment	$ 2,300,000		$ 2,300,000		$ 1,600,000