Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Apr. 30, 2017	Apr. 30, 2016
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (62,374)	$ (63,788)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	14,825	10,432
Stock-based compensation expense	32,219	22,998
Other	451	182
Changes in operating assets and liabilities:
Accounts receivable, net	36,571	28,593
Inventory	(16,105)	(2,623)
Deferred commissions	(362)	4,141
Prepaid expenses and other current assets	(3,944)	(2,744)
Accounts payable	(3,982)	166
Accrued compensation and other liabilities	(19,998)	(11,017)
Deferred revenue	8,398	20,653
Net cash provided by (used in) operating activities	(14,301)	6,993
CASH FLOWS FROM INVESTING ACTIVITIES
Purchases of property and equipment	(12,769)	(24,376)
Purchases of marketable securities	(55,976)	(343,466)
Sales of marketable securities	5,384	23,327
Maturities of marketable securities	46,321	0
Net decrease in restricted cash	0	706
Net cash used in investing activities	(17,040)	(343,809)
CASH FLOWS FROM FINANCING ACTIVITIES
Net proceeds from exercise of stock options	2,257	3,091
Proceeds from issuance of common stock under employee stock purchase plan	14,166	15,079
Net cash provided by financing activities	16,423	18,170
Net decrease in cash and cash equivalents	(14,918)	(318,646)
Cash and cash equivalents, beginning of period	183,675	604,742
Cash and cash equivalents, end of period	168,757	286,096
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION
Cash paid for income taxes	790	1,323
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING INFORMATION
Property and equipment purchased but not yet paid	9,685	9,448
Vesting of early exercised stock options	$ 298	$ 176