Summary of Significant Accounting Policies - Additional Information (Detail)			12 Months Ended
	Jan. 01, 2018 USD ($)	Nov. 30, 2017 USD ($)	Dec. 31, 2018	Dec. 31, 2017 USD ($) Customer	Dec. 31, 2016 USD ($) Customer	Dec. 31, 2015 USD ($)	Apr. 30, 2017 USD ($)	Jan. 27, 2017 USD ($)	Sep. 30, 2016 USD ($)
Deferred cost recognition period				1 year
Short-term Investments				$ 42,900,000	$ 0
Impairment of goodwill		$ 0		0	0	$ 0
Advertising expenses				1,200,000	$ 1,100,000	$ 800,000
Revaluation of deferred tax due to reduction in tax rate				$ 7,200,000
Federal corporate income tax rate				35.00%
Liability on foreign earnings and profits				$ 0
Scenario, Plan
Federal corporate income tax rate			21.00%
Customer Relationships
Acquired finite lived intangible assets, useful life				5 years
Computer and System Software
Property and equipment, useful life in years				3 years
Office Computers
Property and equipment, useful life in years				3 years
Systems Hardware
Property and equipment, useful life in years				5 years
Furniture and Equipment
Property and equipment, useful life in years				5 years
Capitalized software development costs [Member]
Property and equipment, useful life in years				3 years	3 years
IPO
Deferred offering costs							$ 600,000		$ 3,600,000
Customer Concentration Risk | Revenue
Number of customers above 10% threshold | Customer				0	0
Customer Concentration Risk | Accounts Receivable
Number of customers above 10% threshold | Customer				0	0
Crisis Commander | Other Long Term Liabilities
Recognition of obligation					$ 400,000
IDV Solutions LLC
Recognition of obligation				$ 700,000				$ 5,000,000
Acquired finite lived intangible assets, useful life				4 years 3 months 3 days
IDV Solutions LLC | Tradenames
Acquired finite lived intangible assets, useful life				5 years
IDV Solutions LLC | Customer Relationships
Acquired finite lived intangible assets, useful life				5 years
IDV Solutions LLC | Technology
Acquired finite lived intangible assets, useful life				3 years
Minimum | Tradenames
Acquired finite lived intangible assets, useful life				2 years
Minimum | Technology
Acquired finite lived intangible assets, useful life				2 years
Maximum
Cash and cash equivalent, FDIC insured amount				$ 250,000
Maximum | Tradenames
Acquired finite lived intangible assets, useful life				7 years
Maximum | Technology
Acquired finite lived intangible assets, useful life				7 years
ASU No. 2014-09 | Subsequent Event
Deferred cost recognition period	4 years
ASU No. 2014-09 | Minimum | Subsequent Event
Adjustment to decrease accumulated deficit	$ 7,500,000
ASU No. 2014-09 | Maximum | Subsequent Event
Adjustment to decrease accumulated deficit	$ 9,000,000