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Summary of Significant Accounting Policies - Additional Information (Detail)		12 Months Ended
	Nov. 30, 2018 USD ($)	Dec. 31, 2018 USD ($) Customer $ / shares	Dec. 31, 2017 USD ($) Customer	Dec. 31, 2016 USD ($)	Apr. 30, 2017 USD ($)
Restricted cash		$ 90,000	$ 297,000
Short-term investments		45,500,000	42,900,000
Impairment of goodwill	$ 0	$ 0	0	$ 0
Subscription contracts		The Company’s subscription contracts are generally two years or longer in length, billed annually in advance, and non-cancelable.
Advertising expenses		$ 1,400,000	1,200,000	$ 1,100,000
Dividend rate		0.00%
Revaluation of deferred tax due to reduction in tax rate			$ 7,200,000
Federal corporate income tax rate		21.00%	35.00%
Liability on foreign earnings and profits		$ 0
Market-Based Restricted Stock Units
Share Based compensation threshold consecutive trading days		30 days
Risk-free interest rate, minimum		2.26%
Risk-free interest rate, maximum		2.90%
Dividend rate		0.00%
Expected term (in years)		10 years
Expected volatility, minimum		50.00%
Expected volatility, maximum		60.00%
Share-based compensation, vesting stock percentage		125.00%
Performance-Based Restricted Stock Units \| Tranche One
Share-based compensation, compounded annual growth measurement period		2 years
Share-based compensation, vesting stock percentage		50.00%
Performance-Based Restricted Stock Units \| Tranche Two
Share-based compensation, compounded annual growth measurement period		3 years
Incremental and Recoverable Costs
Deferred cost amortization period		4 years
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
Property and equipment, useful life in years		3 years
IPO
Deferred offering costs		$ 300,000			$ 600,000
Deposits and Escrow Fees
Restricted cash		$ 100,000	$ 300,000
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
Minimum
Estimated useful life		1 year
Subscription contracts term		2 years
Minimum \| Market-Based Restricted Stock Units
Share-based compensation, vesting stock price trigger \| $ / shares		$ 35
Minimum \| Performance-Based Restricted Stock Units
Share-based compensation, thresholds percentage of revenue growth		20.00%
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
Estimated useful life		7 years
Maximum \| Market-Based Restricted Stock Units
Share-based compensation, vesting stock price trigger \| $ / shares		$ 65
Maximum \| Performance-Based Restricted Stock Units
Share-based compensation, thresholds percentage of revenue growth		40.00%
Maximum \| Tradenames
Acquired finite lived intangible assets, useful life		8 years
Maximum \| Technology
Acquired finite lived intangible assets, useful life		7 years