CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Cash flows from operating activities
Net loss	$ (96,359)	$ (86,681)	$ (73,486)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	3,703	3,751	4,062
Stock-based compensation	21,235	21,004	12,787
Deferred income taxes	(302)	(4)	(2)
Change in fair value of warrant liability	(101)	(38)	(52)
Change in operating assets and liabilities:
Accounts receivable	(15,901)	(9,263)	(10,123)
Prepaid expenses and other current assets	(2,595)	(450)	(460)
Deferred commissions	(5,545)	(6,019)	(533)
Other long-term assets	(687)	(784)	(27)
Accounts payable	(371)	1,296	371
Deferred rent	(133)	(672)	(681)
Accrued liabilities	8,115	3,948	3,478
Deferred revenue	44,060	35,834	17,705
Net cash used in operating activities	(44,881)	(38,078)	(46,961)
Cash flows from investing activities
Purchases of property and equipment	(2,135)	(1,683)	(468)
Proceeds from maturities of marketable securities	82,230	114,775	38,000
Purchases of marketable securities	(252,382)	(82,036)	(117,954)
Net cash (used in) provided by investing activities	(172,287)	31,056	(80,422)
Cash flows from financing activities
Proceeds from exercise of stock options, including early exercised stock options	8,367	8,220	3,104
Repurchase of early exercised stock options	(242)	(48)	(17)
Proceeds from issuance of Series F financing, net of issuance cost	0	34,942	0
Proceeds from initial public offering, net of underwriting discounts and commissions	205,494	0	0
Proceeds from exercise of redeemable convertible preferred stock warrants	1	0	0
Payment of initial public offering costs	(3,728)	0	0
Net cash provided by financing activities	209,892	43,114	3,087
Effect of exchange rate changes on cash, cash equivalents, and restricted cash	291	7	(92)
Net (decrease) increase in cash, cash equivalents, and restricted cash	(6,985)	36,099	(124,388)
Cash, cash equivalents, and restricted cash, beginning of period	69,412	33,313	157,701
Cash, cash equivalents, and restricted cash, end of period	62,427	69,412	33,313
Cash paid during the period for:
Income taxes, net of refunds	1,004	411	522
Interest	8	16	14
Noncash investing and financing activities
Issuance of Series F redeemable convertible preferred stock warrants	0	0	151
Vesting of early exercised stock options	1,280	903	391
Conversion of redeemable convertible preferred stock warrant liability to redeemable convertible preferred stock as a result of warrant exercise	1,171	0	0
Conversion of redeemable convertible preferred stock to common stock	346,428	0	0
Estimated fair value of office space under a build-to-suit lease	54,709	0	0
Reconciliation of cash, cash equivalents, and restricted cash within the consolidated balance sheets to the amounts shown in the statements of cash flows above:
Total cash, cash equivalents and restricted cash	$ 69,412	$ 33,313	$ 157,701