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	$ (157,659)		$ (105,801)	$ (100,968)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	7,105		9,270	7,753
Stock-based compensation expense	51,818		13,834	9,755
Excess tax benefit from stock-based compensation	0		71	0
Accretion of balloon payment	1,709		603	947
Amortization of debt issuance cost, credit facility fees and debt discounts	241		239	670
Restructuring charges	(974)	[1]	0	0
Other	(16)		(36)	(39)
Changes in operating assets and liabilities:
Accounts receivable	13,027		(10,036)	(4,083)
Inventories	(1,024)		(3,134)	1,821
Prepaid expenses and other assets	550		(1,383)	(645)
Payment of offering costs	(4,253)		(2,348)	0
Accounts payable	(6,354)		7,291	(1,095)
Deferred revenue	5,216		14,581	18,842
Accrued and other liabilities	(1,246)		6,483	4,933
Net cash used in operating activities	(91,860)		(70,366)	(62,109)
Cash flows from investing activities:
Purchase of property and equipment	(6,415)		(4,337)	(10,914)
Purchase of investments	(11,513)		(13,807)	(70,419)
Proceeds from maturities of investments	11,513		76,478	6,350
Proceeds from disposition of investments	0		0	18,574
Net cash provided by (used in) investing activities	(6,415)		58,334	(56,409)
Cash flows from financing activities:
Payment on capital lease financing	(234)		(240)	(300)
Proceeds from issuance of convertible preferred stock, net of issuance costs	0		0	122,770
Proceeds from revolving line of credit	5,000		6,962	7,000
Proceeds from term loan	15,000		0	35,000
Repayment of revolving line of credit	0		0	(6,000)
Proceeds from initial public offering, net of underwriting discounts and commissions	62,314		0	0
Proceeds from repayment of employee notes receivable	0		411	0
Proceeds from exercise of stock options	470		2,292	3,132
Repurchase of common stock	0		0	(5)
Net cash provided by financing activities	82,550		9,425	161,597
Foreign exchange impact on cash and cash equivalents	(42)		(61)	(2)
Net increase (decrease) in cash and cash equivalents	(15,767)		(2,668)	43,077
Cash and cash equivalents, beginning of period	48,048		50,716	7,639
Cash and cash equivalents, end of period	32,281		48,048	50,716
Supplemental disclosures of cash flow information:
Cash paid for income taxes	145		912	361
Cash paid for interest	6,573		4,038	2,411
Supplemental disclosures of noncash investing and financing activities:
Common stock warrants issued to Series E-2 and F-2 holders	14,641		0	0
Conversion of convertible preferred stock to common stock	263,729		0	0
Vesting of early exercised options	891		65	23
Assets acquired through accounts payable	2,157		317	402
Transfer of inventory to sales demonstration equipment	416		140	1,150
Repurchase of common stock by way of note forgiveness	1,211		0	0
Repayment of executive employee promissory notes through repurchase of common stock	7,899		0	0
Series E and E-1 Converible Preferred Stock
Supplemental disclosures of noncash investing and financing activities:
Deemed dividend to series E and E-1 Convertible Preferred Stock	6,588		0	0
Series E, E-1 and F Convertible Preferred Stock
Supplemental disclosures of noncash investing and financing activities:
Impact of adjustment to Series E, E-1 and F Convertible Preferred Stock	$ 26,336		$ 0	$ 0

[1] The non-cash adjustments to restructuring charges primarily consist of the reversal of previously recognized stock-based compensation expense related to awards that will not vest and the reversal of incentive compensation that will not be paid as a result of the restructuring plan.