CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2016	Jul. 31, 2015
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (38,102)	$ (50,175)	$ (76,677)	$ (97,458)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	10,721	9,865	22,805	19,031
Stock-based compensation expense	19,064	14,728	35,153	27,443
Amortization of deferred commissions	4,605	3,922	9,376	7,528
Other	(25)	102	83	100
Changes in operating assets and liabilities, net of effects of acquisitions:
Accounts receivable, net	(17,555)	(15,496)	24,372	127
Deferred commissions	(4,149)	(5,354)	(6,406)	(8,167)
Prepaid expenses and other assets, current and noncurrent	2,664	1,343	2,437	(27,112)
Accounts payable	(550)	8,602	(284)	8,868
Accrued expenses and other liabilities	7,484	2,560	(19,214)	1,563
Deferred rent	144	2,094	2,654	3,942
Deferred revenue	10,820	6,148	(3,409)	10,292
Net cash used in operating activities	(4,879)	(21,661)	(9,110)	(53,843)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of marketable securities	0	(6,202)	0	(112,521)
Sales of marketable securities	240	709	240	3,849
Maturities of marketable securities	471	6,653	7,057	6,653
Purchases of property and equipment	(771)	(17,943)	(11,747)	(27,844)
Proceeds from sale of property and equipment	72	0	76	0
Acquisitions and purchases of intangible assets, net of cash acquired	0	(18)	0	(218)
Net cash provided by (used in) investing activities	12	(16,801)	(4,374)	(130,081)
CASH FLOWS FROM FINANCING ACTIVITIES:
Payment of initial public offering costs	0	(839)	0	(2,172)
Payment of borrowing costs	0	0	(93)	0
Proceeds from exercise of stock options, net of repurchases of early exercised stock options	1,969	1,618	4,215	2,414
Proceeds from issuances of common stock under employee stock purchase plan	0	0	9,016	0
Employee payroll taxes paid related to net share settlement of restricted stock units	(4,100)	(1,972)	(8,868)	(6,187)
Payments of capital lease obligations	(2,312)	(192)	(3,261)	(420)
Net cash provided by (used in) financing activities	(4,443)	(1,385)	1,009	(6,365)
Effect of exchange rate changes on cash and cash equivalents	(49)	(21)	65	(28)
Net decrease in cash and cash equivalents	(9,359)	(39,868)	(12,410)	(190,317)
Cash and cash equivalents, beginning of period	182,690	179,987	185,741	330,436
Cash and cash equivalents, end of period	173,331	140,119	173,331	140,119
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:
Cash paid for interest, net of amounts capitalized	555	293	788	652
Net cash paid (received) for income taxes, net of tax refunds	(2)	242	116	700
SUPPLEMENTAL DISCLOSURE OF NONCASH INVESTING AND FINANCING ACTIVITIES:
Change in accrued equipment purchases	(2,180)	8,446	(15,024)	5,648
Purchases of property and equipment under capital lease	5,562	2,335	9,910	4,065
Change in unpaid tax related to capital lease	628	0	430	0
Change in unpaid taxes related to net share settlement of restricted stocks	(461)	0	0	0
Vesting of early exercised stock options and restricted stock	0	40	11	80
Issuance of common stock in connection with acquisitions and purchases of intangible assets	0	5,444	0	6,108
Change in unpaid deferred offering costs	$ 0	$ (839)	$ 0	$ (2,172)