Common Stock and Stockholders' Equity (Deficit) - Narrative (Details) $ / shares in Units, $ in Thousands		12 Months Ended
	Apr. 06, 2017 shares	Jan. 31, 2018 USD ($) vote $ / shares shares	Jan. 31, 2017 USD ($) $ / shares shares	Jan. 31, 2016 USD ($) shares
Class of Stock [Line Items]
Redeemable preferred stock outstanding (in shares)		0	0
Redeemable convertible preferred stock, shares issued (in shares)		0	59,465,439
Shares authorized (in shares)			120,000,000
Common stock, par value (in dollars per share) | $ / shares			$ 0.0001
Non-cash charitable contributions | $		$ 708	$ 0	$ 0
Series B Redeemable Convertible Preferred Stock
Class of Stock [Line Items]
Shares issuable under warrants granted (in shares)			29,058
Shares issuable under warrants granted (in dollars per share) | $ / shares			$ 1.38
Fair value of warrant | $			$ 300
Redeemable Convertible Preferred Stock
Class of Stock [Line Items]
Redeemable convertible preferred stock converted to common class B stock (in shares)	59,491,640
Redeemable preferred stock outstanding (in shares)		0
Redeemable convertible preferred stock, shares issued (in shares)		0
Class B Common Stock
Class of Stock [Line Items]
Common class B stock after conversion of redeemable convertible stock (in shares)	59,491,640
Shares authorized (in shares)		120,000,000	120,000,000
Common stock, par value (in dollars per share) | $ / shares		$ 0.0001	$ 0.0001
Common stock outstanding (in shares)		33,361,106	20,229,000
Number of votes per share | vote		10
Non-cash charitable contributions | $			$ 100	$ 100
Series B Redeemable Convertible Preferred Stock
Class of Stock [Line Items]
Redeemable convertible preferred stock, shares issued (in shares)			11,986,055
Class A Common Stock
Class of Stock [Line Items]
Shares authorized (in shares)		1,000,000,000	0
Common stock, par value (in dollars per share) | $ / shares		$ 0.0001	$ 0.0001
Common stock outstanding (in shares)		70,609,898	0
Number of votes per share | vote		1
Non-cash charitable contributions | $		$ 700
Common Stock | Class B Common Stock
Class of Stock [Line Items]
Issuance of common stock pursuant to charitable donation (in shares)		0	13,935	17,433
Common Stock | Class A Common Stock
Class of Stock [Line Items]
Issuance of common stock pursuant to charitable donation (in shares)		24,287