Property and Equipment, Net (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property and equipment	$ 124,394		$ 124,394		$ 98,906
Less: accumulated depreciation and amortization	(73,113)		(73,113)		(59,505)
Property and equipment, net	51,281		51,281		39,401
Depreciation and amortization expense	5,100	$ 4,400	14,700	$ 12,000
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment	70,158		70,158		57,295
Computer software
Property, Plant and Equipment [Line Items]
Property and equipment	20,254		20,254		19,716
Furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Property and equipment	4,025		4,025		3,425
Scanner appliances
Property, Plant and Equipment [Line Items]
Property and equipment	14,419		14,419		14,776
Scanner appliances and other computer equipment subject to subscription
Property, Plant and Equipment [Line Items]
Property and equipment, net	7,700		7,700		8,300
Scanner appliances and other computer equipment not placed in service
Property, Plant and Equipment [Line Items]
Property and equipment	1,700		1,700		1,300
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment	$ 15,538		$ 15,538		$ 3,694