CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2017	Oct. 31, 2016
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (42,924)	$ (38,233)	$ (122,295)	$ (114,910)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	9,913	8,710	29,250	31,515
Stock-based compensation expense	25,523	19,917	72,536	55,070
Amortization of deferred commissions	5,393	4,251	15,751	13,627
Other	(124)	13	(83)	96
Changes in operating assets and liabilities:
Accounts receivable, net	12,023	(10,825)	24,245	13,547
Deferred commissions	(4,616)	(3,667)	(13,235)	(10,073)
Prepaid expenses, restricted cash and other assets	2,746	1,670	(2,959)	4,107
Accounts payable	(2,592)	2,353	4,469	2,069
Accrued expenses and other liabilities	(4,828)	(1,036)	(8,721)	(20,250)
Deferred rent	1,413	424	3,132	3,078
Deferred revenue	12,167	9,594	11,022	6,185
Net cash provided by (used in) operating activities	14,094	(6,829)	13,112	(15,939)
CASH FLOWS FROM INVESTING ACTIVITIES:
Sales of marketable securities				240
Maturities of marketable securities				7,057
Purchases of property and equipment	(3,003)	(1,892)	(4,800)	(13,639)
Proceeds from sale of property and equipment	2	8	31	84
Net cash used in investing activities	(3,001)	(1,884)	(4,769)	(6,258)
CASH FLOWS FROM FINANCING ACTIVITIES:
Payment of borrowing costs				(93)
Proceeds from exercise of stock options, net of repurchases of early exercised stock options	4,002	3,388	9,415	7,603
Proceeds from issuances of common stock under employee stock purchase plan	8,640	6,710	17,521	15,726
Employee payroll taxes paid related to net share settlement of restricted stock units	(11,284)	(4,726)	(26,219)	(13,594)
Acquisition related contingent consideration			(991)
Payments of capital lease obligations	(4,781)	(2,178)	(12,693)	(5,439)
Net cash (used in) provided by financing activities	(3,423)	3,194	(12,967)	4,203
Effect of exchange rate changes on cash and cash equivalents	(88)	(12)	90	53
Net increase (decrease) in cash and cash equivalents	7,582	(5,531)	(4,534)	(17,941)
Cash and cash equivalents, beginning of period	165,275	173,331	177,391	185,741
Cash and cash equivalents, end of period	172,857	167,800	172,857	167,800
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:
Cash paid for interest, net of amounts capitalized	527	50	1,416	838
Cash paid for income taxes, net of tax refunds	425	95	1,158	211
SUPPLEMENTAL DISCLOSURE OF NONCASH INVESTING AND FINANCING ACTIVITIES:
Change in accrued equipment purchases	1,714	3,647	2,604	(11,377)
Purchases of property and equipment under capital lease	6,194	8,390	21,875	18,300
Change in unpaid tax related to capital lease	160	522	595	952
Vesting of early exercised stock options and restricted stock units				11
Issuance of common stock in connection with acquisitions and purchases of intangible assets		$ 1,011		$ 1,011
Timing of settlement of stock options exercise	$ 520		$ 520