Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2014
Cash flows from operating activities
Net income	$ 54,460	$ 40,383	$ 23,615
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	8,464	3,929	2,410
Amortization of premiums on short-term investments	2,804	2,176	364
Stock-based compensation	24,258	14,325	6,950
Deferred income taxes	(6,264)	(4,268)	(1,781)
Bad debt expense	201	227	35
Changes in operating assets and liabilities:
Accounts receivable	(46,653)	(34,455)	(19,738)
Income taxes	(2,994)	3,326	(4,784)
Prepaid expenses and other current and long-term assets	180	(4,652)	(2,951)
Accounts payable	(494)	1,290	(1,303)
Accrued expenses and other current liabilities	5,042	(754)	9,690
Deferred revenue	39,357	45,580	28,473
Other long-term liabilities	1,793	467	773
Net cash provided by operating activities	80,154	67,574	41,753
Cash flows from investing activities
Purchases of short-term investments	(313,357)	(401,955)	(21,403)
Maturities and sales of short-term investments	364,968	156,860	9,700
Purchases of property and equipment	(21,153)	(26,531)	(1,860)
Acquisitions, net of cash acquired	(126,183)		(12,149)
Purchases of intangible assets	(568)
Capitalized internal-use software development costs	(431)	(413)	(1,117)
Proceeds from note receivable–related party			253
Changes in restricted cash and deposits	41	21
Net cash used in investing activities	(96,683)	(272,018)	(26,576)
Cash flows from financing activities
Proceeds from early exercise of common stock options	10		229
Proceeds from exercise of common stock options	5,875	5,813	514
Net proceeds from offerings		34,172	214,523
Proceeds from Employee Stock Purchase Plan		5,951
Restricted stock units acquired to settle employee tax withholding liability	(6)	(15)
Excess tax benefits from employee stock plans	13,527	25,341	174
Net cash provided by financing activities	19,406	71,262	215,440
Effect of exchange rate changes on cash and cash equivalents	49	(72)
Net change in cash and cash equivalents	2,926	(133,254)	230,617
Cash and cash equivalents at beginning of period	129,253	262,507	31,890
Cash and cash equivalents at end of period	132,179	129,253	262,507
Supplemental disclosures of other cash flow information:
Cash paid for income taxes, net of refunds	19,968	1,515	20,673
Non-cash investing and financing activities:
Changes in accounts payable and accrued liabilities related to property and equipment purchases	334	688	18
Vesting of early exercised stock options	70	$ 377	572
Offering costs not yet paid			$ 323
Zinc Ahead Inc [Member]
Non-cash investing and financing activities:
Working capital adjustment, not yet paid	$ 339