Consolidated Statements of Cash Flows - USD ($) $ in Thousands		12 Months Ended
		Jan. 31, 2019		Jan. 31, 2018		Jan. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss		$ (178,362)		$ (159,878)	[1],[2],[3]	$ (221,532)	[1],[2],[3]
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization		70,878		61,744	[1]	50,203	[1]
Amortization of debt discount and debt issuance costs		21,031		0	[1]	0	[1]
Stock-based compensation expense		210,645		150,673	[1]	116,668	[1]
Deferred income tax		(3,696)		(216)	[1]	(308)	[1]
Other		(1,343)		2,270	[1]	1,892	[1]
Changes in operating assets and liabilities, net of effects of acquisition:
Accounts receivable, net		(135,649)		(74,505)	[1]	(44,049)	[1]
Inventory		(12,289)		(12,595)	[1]	(3,776)	[1]
Deferred commissions		(27,660)		(27,978)	[1]	(13,080)	[1]
Prepaid expenses and other assets		(6,972)		(23,799)	[1]	(6,133)	[1]
Accounts payable		14,293		29,278	[1]	10,644	[1]
Accrued compensation and other liabilities		51,810		26,622	[1]	19,381	[1]
Deferred revenue		161,737		101,140	[1]	75,728	[1]
Net cash provided by (used in) operating activities		164,423		72,756	[1]	(14,362)	[1]
CASH FLOWS FROM INVESTING ACTIVITIES
Purchases of property and equipment		(100,246)		(65,060)	[1]	(76,773)	[1]
Acquisition, net of cash acquired		(13,899)		0	[1]	0	[1]
Purchase of other investment		(5,000)		0	[1]	0	[1]
Purchase of intangible assets		0		0	[1]	(1,000)	[1]
Purchases of marketable securities		(665,357)		(202,656)	[1]	(526,717)	[1]
Sales of marketable securities		19,878		66,489	[1]	114,354	[1]
Maturities of marketable securities		253,280		144,068	[1]	48,513	[1]
Net cash used in investing activities		(511,344)		(57,159)	[1]	(441,623)	[1]
CASH FLOWS FROM FINANCING ACTIVITIES
Net proceeds from exercise of stock options		47,771		24,677	[1]	14,912	[1]
Proceeds from issuance of common stock under employee stock purchase plan		33,444		22,137	[1]	25,606	[1]
Proceeds from issuance of convertible senior notes, net of issuance costs		562,062		0	[1]	0	[1]
Payment for purchase of capped calls		(64,630)		0	[1]	0	[1]
Repayment of debt assumed from acquisition		(6,101)		0	[1]	0	[1]
Tax withholding on vesting of restricted stock		(632)		0		0
Repurchase of common stock		(20,000)		0	[1]	0	[1]
Net cash provided by financing activities		551,914		46,814	[1]	40,518	[1]
Net increase (decrease) in cash, cash equivalents and restricted cash		204,993		62,411	[1]	(415,467)	[1]
Cash, cash equivalents and restricted cash, beginning of year		463,813		258,820	[1]	196,409	[1]
Cash, cash equivalents and restricted cash, end of year		463,813		258,820	[1]	196,409	[1]
Cash and cash equivalents	[1]	244,057	[4]	183,675
Cash, cash equivalents and restricted cash, end of year		447,990		244,057	[1],[4]	183,675	[1]
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION
Cash paid for interest		371		0		0
Cash paid for income taxes		4,696		3,090	[1]	2,866	[1]
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING INFORMATION
Property and equipment purchased but not yet paid		13,873		9,940	[1]	7,414	[1]
Acquisition consideration held back to satisfy potential indemnification claims		3,725		0	[1]	0	[1]
Vesting of early exercised stock options		$ 320		$ 1,042	[1]	$ 3,399	[1]

[1] * As adjusted to reflect the impact of ASU 2016-18 and the full retrospective adoption of

[2] * As adjusted to reflect the impact of the full retrospective adoption of ASC 606 - see Note 2.

[3] *As adjusted to reflect the impact of the full retrospective adoption of ASC 606 - see Note 2.

[4] * As adjusted to reflect the impact of the full retrospective adoption of ASC 606