Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2015	Jul. 31, 2014	Jul. 31, 2015	Jul. 31, 2014
Cash flows from operating activities
Net income	$ 13,406	$ 9,578	$ 26,388	$ 16,799
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	1,344	991	2,368	1,921
Amortization of premiums on short-term investments	750	421	1,513	733
Stock-based compensation	5,611	3,400	10,410	6,656
Bad debt expense	245	41	238	69
Changes in operating assets and liabilities:
Accounts receivable	1,995	(721)	25,531	(3,533)
Income taxes	(3,019)	(280)	(157)	(2,958)
Prepaid expenses and other current and long-term assets	(5,560)	511	(5,527)	(1,350)
Accounts payable	560	(1,210)	(200)	(298)
Accrued expenses and other current liabilities	1,673	(6,544)	337	(1,226)
Deferred revenue	(1,651)	10,431	(3,848)	17,923
Other long-term liabilities	(172)	(10)	(80)	2
Net cash provided by operating activities	15,182	16,608	56,973	34,738
Cash flows from investing activities
Purchases of short-term investments	(67,078)	(94,776)	(167,915)	(229,892)
Maturities and sales of short-term investments	69,008	40,763	116,752	44,630
Purchases of property and equipment	(9,782)	(24,983)	(14,492)	(25,282)
Acquisitions, net of cash acquired	(7)		(9,994)
Purchases of intangible assets	(568)		(568)
Capitalized internal-use software development costs	(172)		(194)	(220)
Changes in restricted cash and deposits	2	4	3	1
Net cash used in investing activities	(8,597)	(78,992)	(76,408)	(210,763)
Cash flows from financing activities
Proceeds from early exercise of common stock options	2		10
Proceeds from exercise of common stock options	1,608	1,527	2,770	2,212
Net proceeds from offerings		(499)		34,495
Proceeds from Employee Stock Purchase Plan		5,951		5,951
Restricted stock units acquired to settle employee tax withholding liability	(2)		(6)
Excess tax benefits from employee stock plans	3,982	6,654	7,151	11,033
Net cash provided by financing activities	5,590	13,633	9,925	53,691
Effect of exchange rate changes on cash and cash equivalents	40	(21)	33	(57)
Net change in cash and cash equivalents	12,215	(48,772)	(9,477)	(122,391)
Cash and cash equivalents at beginning of period	107,561	188,888	129,253	262,507
Cash and cash equivalents at end of period	119,776	140,116	119,776	140,116
Supplemental disclosures of other cash flow information:
Cash paid for income taxes, net of refunds	13,350	706	15,992	4,624
Non-cash investing and financing activities:
Changes in accounts payable and accrued liabilities related to property and equipment purchases	133	(90)	2,615	(21)
Vesting of early exercised stock options	18	112	35	$ 231
Offering costs not yet paid		$ (515)
Acquisition escrow settlement, not yet received	$ 300		$ 300