Property and Equipment, Net (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property and equipment	$ 191,109		$ 183,893
Finance leases - right of use asset	1,007		1,299
Less: accumulated depreciation and amortization	(129,444)		(123,314)
Property and equipment, net	61,665		60,579
Depreciation and amortization expense	6,100	$ 6,400
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment, net	116,810		112,599
Computer software
Property, Plant and Equipment [Line Items]
Property and equipment, net	26,154		26,137
Furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Property and equipment, net	8,133		6,973
Finance leases - right of use asset
Property, Plant and Equipment [Line Items]
Property and equipment, net	3,503		3,503
Scanner appliances
Property, Plant and Equipment [Line Items]
Property and equipment, net	16,207		15,864
Scanner appliances and other computer equipment subject to subscription
Property, Plant and Equipment [Line Items]
Property and equipment, net	4,400		4,900
Scanner appliances and other computer equipment not placed in service
Property, Plant and Equipment [Line Items]
Property and equipment	800		900
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, net	$ 20,302		$ 18,817