CONDENSED CONSOLIDATED STATEMENT OF STOCKHOLDERS’ EQUITY - 6 months ended Jul. 31, 2018 - USD ($) $ in Thousands	Total	Class A and Class B Common Stock	Additional Paid-In Capital	Treasury Stock	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning balance (in shares) at Jan. 31, 2018		50,575,571
Beginning balance at Jan. 31, 2018	$ 193,493	$ 51	$ 638,680	$ (1,319)	$ (159)	$ (443,760)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises (in shares)	1,191,587	1,191,587
Stock option exercises	$ 8,078	$ 1	8,077
Repurchase of early exercised options (in shares)		(33,395)
Repurchase of early exercised options	0
Vesting of early exercised stock options	835		835
Vesting of restricted stock units (in shares)		75,603
Vesting of restricted stock units	0	$ 0	0
Stock-based compensation	16,586		16,586
Issuance of common stock under the Employee Stock Purchase Plan (in shares)		275,874
Issuance of common stock under the Employee Stock Purchase Plan	5,626		5,626
Equity component of convertible senior notes	81,683		81,683
Purchase of capped calls	(37,086)		(37,086)
Unrealized gain on available-for-sale securities	(52)				(52)
Foreign currency translation adjustment	(129)				(129)
Net loss	(60,410)					(60,410)
Ending balance (in shares) at Jul. 31, 2018		52,085,240
Ending balance at Jul. 31, 2018	$ 208,624	$ 52	$ 714,401	$ (1,319)	$ (340)	$ (504,170)