Description of Operations and Summary of Significant Accounting Policies - Additional Information (Details)	1 Months Ended	12 Months Ended
	Sep. 30, 2016 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) Segment shares	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 USD ($)	Apr. 30, 2016 USD ($)
Description Of Operations And Summary Of Significant Accounting Policies [Line Items]
Common stock, shares outstanding | shares			12,897,001
Deferred offering costs		$ 3,698,000
Accumulated deficit		$ (200,324,000)	$ (168,771,000)
Number of operating segment | Segment		1
Restricted cash		$ 0	2,500,000		$ 2,500,000
Advertising expenses		7,400,000	7,500,000	$ 6,500,000
Interest expense capitalized		0	0	0
Software development costs capitalized		1,100,000	$ 800,000	$ 500,000
Payment of debt prepayment fees		$ 200,000
Customer Concentration Risk | Accounts Receivable | Customer One
Description Of Operations And Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage			10.50%
Class A Common Stock
Description Of Operations And Summary Of Significant Accounting Policies [Line Items]
Conversion ratio		100.00%
Common stock, shares outstanding | shares		6,900,000
Common Class B Converted From Common
Description Of Operations And Summary Of Significant Accounting Policies [Line Items]
Conversion ratio	100.00%
Common Class B Converted From Common Stock Warrants
Description Of Operations And Summary Of Significant Accounting Policies [Line Items]
Conversion ratio	100.00%
Warrants outstanding | shares	47,893
Common Class B Converted From Convertible Preferred Stock Warrant
Description Of Operations And Summary Of Significant Accounting Policies [Line Items]
Conversion ratio	100.00%
Warrants outstanding | shares	27,321
Convertible Preferred Stock
Description Of Operations And Summary Of Significant Accounting Policies [Line Items]
Conversion of preferred stock to Class B common stock, Shares | shares	18,239,475	(18,240,000)
Class B Common Stock
Description Of Operations And Summary Of Significant Accounting Policies [Line Items]
Conversion ratio		100.00%
Common stock, shares outstanding | shares		31,437,741
IPO
Description Of Operations And Summary Of Significant Accounting Policies [Line Items]
Deferred offering costs		$ 3,698,000
IPO | Class A Common Stock
Description Of Operations And Summary Of Significant Accounting Policies [Line Items]
Shares sold (in shares) | shares	6,900,000
Share price (in dollars per share) | $ / shares	$ 16.00
Net proceeds after deducting underwriting discounts and commissions and offering expenses	$ 99,000,000