Accounting Standards and Significant Accounting Policies - Schedule of Impact of New Accounting Pronouncements (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Apr. 30, 2018	Apr. 30, 2017		Jan. 31, 2018
Revenue:
Subscription	$ 76,841	$ 48,279	[1]
Professional services and other	6,780	4,046	[1]
Total revenue	83,621	52,325	[1]
Gross profit	59,514	34,862	[1]
Operating expenses:
Sales and marketing	49,493	35,303	[1]
Total operating expenses	84,492	62,301	[1]
Loss before provision for (benefit from) income taxes	(26,193)	(27,458)	[1]
Net loss	$ (25,962)	$ (27,706)	[1],[2],[3]
Net loss per share, basic and diluted (in dollars per share)	$ (0.25)	$ (0.70)	[1]
Current assets:
Deferred commissions	$ 18,551			$ 17,755	[4]
Prepaid expenses and other current assets	20,203			17,781	[4]
Total current assets	636,163			317,498	[4]
Deferred commissions, noncurrent	41,077			40,755	[4]
Total assets	726,904			399,263	[4]
Current liabilities:
Deferred revenue	173,548			159,816	[4]
Total current liabilities	202,926			187,943	[4]
Deferred revenue, noncurrent	4,346			4,963	[4]
Total liabilities	477,287			199,923	[4]
Accumulated deficit	(392,676)			(366,714)	[4]
Total stockholders’ equity	249,617			199,340	[4]
Total liabilities and stockholders’ equity	$ 726,904			399,263	[4]
As Reported
Revenue:
Subscription		$ 48,357
Professional services and other		4,650
Total revenue		53,007
Gross profit		35,544
Operating expenses:
Sales and marketing		37,180
Total operating expenses		64,178
Loss before provision for (benefit from) income taxes		(28,653)
Net loss		$ (28,901)
Net loss per share, basic and diluted (in dollars per share)		$ (0.73)
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
Accounting Standards Update 2014-09 | Adjustments
Revenue:
Subscription		$ (78)
Professional services and other		(604)
Total revenue		(682)
Gross profit		(682)
Operating expenses:
Sales and marketing		(1,877)
Total operating expenses		(1,877)
Loss before provision for (benefit from) income taxes		1,195
Net loss		$ 1,195
Net loss per share, basic and diluted (in dollars per share)		$ 0.03
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

[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.