Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2017	Jul. 31, 2016
Cash flows from operating activities
Net income		$ 37,844	$ 12,958	$ 73,867	$ 25,467
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization		3,571	3,470	7,020	6,875
Amortization of premiums on short-term investments		386	469	842	889
Stock-based compensation		13,380	10,014	25,168	18,157
Deferred income taxes		(708)	36	(1,905)	(802)
Loss on foreign currency from market-to-market derivative		204		253
Bad debt expense		(198)	90	(206)	(115)
Changes in operating assets and liabilities:
Accounts receivable		16,169	(7,277)	85,869	55,950
Income taxes		483	1,264	(2,062)	1,644
Prepaid expenses and other current and long-term assets		332	(9,466)	(1,159)	(8,076)
Accounts payable		700	1,805	244	1,871
Accrued expenses and other current liabilities		(361)	1,800	544	(1,105)
Deferred revenue		(15,410)	(4,058)	9,027	19,299
Other long-term liabilities		1,215	641	2,266	1,052
Net cash provided by operating activities	[1]	57,607	11,746	199,768	121,106
Cash flows from investing activities
Purchases of short-term investments		(87,202)	(116,219)	(143,451)	(183,959)
Maturities and sales of short-term investments		69,681	58,151	128,377	128,176
Purchases of property and equipment		(2,535)	(859)	(6,495)	(2,916)
Capitalized internal-use software development costs		(242)	(69)	(1,033)	(209)
Changes in restricted cash and deposits		(201)	109	(202)	103
Net cash (used in) investing activities		(20,499)	(58,887)	(22,804)	(58,805)
Cash flows from financing activities
Proceeds from exercise of common stock options		6,131	3,183	13,416	4,528
Restricted stock units acquired to settle employee tax withholding liability			(11)		(12)
Excess tax benefits from employee stock plans			8,079		10,940
Net cash provided by financing activities	[1]	6,131	11,251	13,416	15,456
Effect of exchange rate changes on cash and cash equivalents		327	313	1,240	429
Net change in cash and cash equivalents		43,566	(35,577)	191,620	78,186
Cash and cash equivalents at beginning of period		365,660	245,942	217,606	132,179
Cash and cash equivalents at end of period		409,226	210,365	409,226	210,365
Supplemental disclosures of other cash flow information:
Cash paid for income taxes, net of refunds		1,780	9,316	6,036	12,281
Non-cash investing and financing activities:
Changes in accounts payable and accrued expenses related to property and equipment purchases		$ 465	(98)	(121)	(787)
Vesting of early exercised stock options			$ 10	$ 1	$ 26

[1] During the six months ended July 31, 2017, the Company adopted Accounting Standards Update (“ASU”) 2016-09, “Compensation-Stock Compensation: Improvements to Employee Share-Based Payment.” Refer to note 1—New Accounting Pronouncements Adopted in Fiscal 2018 for further details. This adoption resulted in a $14.8 million and $28.7 million increase in net cash provided by operating activities and a corresponding decrease in net cash provided by financing activities for the three and six months ended July 31, 2017, respectively.