Accounting Standards and Significant Accounting Policies - Schedule of Impact of New Accounting Pronouncements (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended			9 Months Ended
	Oct. 31, 2018	Oct. 31, 2017		Oct. 31, 2018	Oct. 31, 2017		Jan. 31, 2018
Revenue:
Total revenue	$ 105,576	$ 66,911	[1]	$ 283,783	$ 179,495	[1]
Gross profit	75,876	45,788	[1]	201,748	121,227	[1]
Operating expenses:
Sales and marketing	56,911	47,567	[1]	165,408	120,761	[1]
Total operating expenses	104,355	80,303	[1]	293,635	209,366	[1]
Loss before provision for (benefit from) income taxes	(30,184)	(34,006)	[1]	(96,569)	(87,267)	[1]
Net loss	$ (29,517)	$ (33,066)	[1],[2]	$ (94,686)	$ (86,804)	[1],[3]
Net loss per share, basic and diluted (in dollars per share)	$ (0.27)	$ (0.35)	[1]	$ (0.89)	$ (1.13)	[1]
Current assets:
Deferred commissions	$ 21,695			$ 21,695			$ 17,755	[4]
Prepaid expenses and other current assets	20,280			20,280			17,781	[4]
Total current assets	658,114			658,114			317,498	[4]
Deferred commissions, noncurrent	47,756			47,756			40,755	[4]
Total assets	796,709			796,709			399,263	[4]
Current liabilities:
Deferred revenue	206,146			206,146			159,816	[4]
Total current liabilities	244,786			244,786			187,943	[4]
Deferred revenue, noncurrent	4,977			4,977			4,963	[4]
Total liabilities	552,206			552,206			199,923	[4]
Accumulated deficit	(461,400)			(461,400)			(366,714)	[4]
Total stockholders’ equity	244,503			244,503			199,340	[4]
Total liabilities and stockholders’ equity	796,709			796,709			399,263	[4]
As Reported
Revenue:
Total revenue		$ 68,238			$ 182,240
Gross profit		47,115			123,972
Operating expenses:
Sales and marketing		49,606			126,383
Total operating expenses		82,342			214,988
Loss before provision for (benefit from) income taxes		(34,718)			(90,144)
Net loss		$ (33,778)			$ (89,681)
Net loss per share, basic and diluted (in dollars per share)		$ (0.35)			$ (1.17)
Current assets:
Deferred commissions							16,481
Prepaid expenses and other current assets							16,973
Total current assets							315,416
Deferred commissions, noncurrent							10,971
Total assets							367,397
Current liabilities:
Deferred revenue							162,633
Total current liabilities							190,760
Deferred revenue, noncurrent							6,034
Total liabilities							203,811
Accumulated deficit							(402,468)
Total stockholders’ equity							163,586
Total liabilities and stockholders’ equity							367,397
Adjustments | Accounting Standards Update 2014-09
Revenue:
Total revenue		$ (1,327)			$ (2,745)
Gross profit		(1,327)			(2,745)
Operating expenses:
Sales and marketing		(2,039)			(5,622)
Total operating expenses		(2,039)			(5,622)
Loss before provision for (benefit from) income taxes		712			2,877
Net loss		$ 712			$ 2,877
Net loss per share, basic and diluted (in dollars per share)		$ 0.00			$ 0.04
Current assets:
Deferred commissions							1,274
Prepaid expenses and other current assets							808
Total current assets							2,082
Deferred commissions, noncurrent							29,784
Total assets							31,866
Current liabilities:
Deferred revenue							(2,817)
Total current liabilities							(2,817)
Deferred revenue, noncurrent							(1,071)
Total liabilities							(3,888)
Accumulated deficit							35,754
Total stockholders’ equity							35,754
Total liabilities and stockholders’ equity							$ 31,866
Subscription
Revenue:
Total revenue	97,698	$ 61,863	[1]	262,393	$ 165,459	[1]
Subscription | As Reported
Revenue:
Total revenue		62,705			167,142
Subscription | Adjustments | Accounting Standards Update 2014-09
Revenue:
Total revenue		(842)			(1,683)
Professional services and other
Revenue:
Total revenue	$ 7,878	5,048	[1]	$ 21,390	14,036	[1]
Professional services and other | As Reported
Revenue:
Total revenue		5,533			15,098
Professional services and other | Adjustments | Accounting Standards Update 2014-09
Revenue:
Total revenue		$ (485)			$ (1,062)

[1] See Note 2 for a summary of adjustments.

[2] See Note 2 for a summary of adjustments.

[3] See Note 2 for a summary of adjustments.

[4] See Note 2 for a summary of adjustments.