Common Stock and Stockholders' Equity (Deficit) - Additional Information (Details)	1 Months Ended	12 Months Ended			132 Months Ended
	Sep. 30, 2016 $ / shares shares	Jan. 31, 2017 USD ($) Vote Period $ / shares shares	Jan. 31, 2016 USD ($) $ / shares shares	Jan. 31, 2015 USD ($) $ / shares	Jan. 31, 2017 USD ($) Vote $ / shares shares	Oct. 05, 2016 shares
Class Of Stock [Line Items]
Common stock voting rights		Each share of common stock has the right to one vote.
Number of common stock voting rights | Vote		1			1
Dividends declared | $					$ 0
Dividends paid | $					$ 0
Preferred stock, shares authorized		25,000,000	0		25,000,000
Preferred stock, par value | $ / shares		$ 0.0001	$ 0.0001		$ 0.0001
Preferred stock, shares issued		0	0		0
Preferred stock, shares outstanding		0	0		0
Aggregate intrinsic value of exercised options | $		$ 11,000,000	$ 5,500,000	$ 2,600,000
Weighted-average grant date fair value of options granted | $ / shares		$ 4.65	$ 2.28	$ 1.24
Total grant date fair value of options vested | $		$ 5,800,000	$ 2,400,000	$ 1,200,000
Number of unvested shares subject to repurchase due to early exercises of options		255,529	208,008		255,529
Total stock-based compensation expense recognized | $		$ 9,452,000	$ 10,568,000	$ 1,807,000
2016 Employee Stock Purchase Plan
Class Of Stock [Line Items]
Common stock reserved for issuance		818,750			818,750
Increase in number of shares reserved for issuance as percentage of outstanding shares of common stock on last day of prior fiscal year		1.00%
Increase in common stock reserved for issuance		1,250,000			1,250,000
Duration of maximum offering period		27 months
Initial offering period end date		Sep. 15, 2018
Duration of new offering period		24 months
Number of consecutive purchase periods | Period		4
Duration of consecutive purchase period		6 months
Maximum percentage of eligible compensation for participants to purchase common stock through payroll deductions		15.00%			15.00%
Purchase price for each share of common stock as percentage of lower of fair market value per share on first day of applicable offering period		85.00%
Number of shares of common stock purchased		0
Total unrecognized compensation cost | $		$ 8,100,000			$ 8,100,000
Total unrecognized compensation cost, weighted-average amortization period		1 year 7 months 13 days
Accrued Expenses and Other Current Liabilities
Class Of Stock [Line Items]
Early exercises of stock options | $		$ 2,600,000	1,100,000		$ 2,600,000
Capitalized Software Development Costs
Class Of Stock [Line Items]
Stock-based compensation capitalized in capitalized software development costs | $		$ 224,000	$ 125,000
Non-employee Consultants
Class Of Stock [Line Items]
Number of options granted		83,500	16,250
2016 Equity Incentive Plan
Class Of Stock [Line Items]
Common stock reserved for issuance						4,500,000
Increase in number of shares reserved for issuance as percentage of outstanding shares of common stock on last day of prior fiscal year		5.00%
2006 Plan
Class Of Stock [Line Items]
Common stock reserved for issuance						13,750,000
2006 Equity Plan | Chief Executive Officer | Market-based Options
Class Of Stock [Line Items]
Number of options granted	544,127
Stock options granted, exercise price | $ / shares	$ 13.04
Stock option vesting period	4 years
Total stock-based compensation expense recognized | $		$ 417,000
Stock option, number of shares vested and exercisable		18,137			18,137
2006 Stock Plan and 2016 Equity Incentive Plan
Class Of Stock [Line Items]
Number of options granted		5,573,721
Stock options granted, exercise price | $ / shares		$ 9.75
Total unrecognized compensation cost related to unvested stock options | $		$ 22,700,000			$ 22,700,000
2006 Stock Plan and 2016 Equity Incentive Plan | Stock Options
Class Of Stock [Line Items]
Total unrecognized compensation cost, weighted-average amortization period		2 years 7 months 28 days