Basis of Presentation and Summary of Significant Accounting Policies - Recently Adopted Accounting Pronouncements (Statement of Operations) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Apr. 30, 2018	Apr. 30, 2017
Revenue:
Product	$ 195,449	$ 142,850	[1]
Support subscription	60,496	39,795	[1]
Total revenue	255,945	182,645	[1]
Gross profit	166,315	119,097	[1]
Sales and marketing	122,367	91,763	[1]
Total operating expenses	228,189	177,287	[1]
Loss from operations	(61,874)	(58,190)	[1]
Loss before provision for income taxes	(62,873)	(56,195)	[1]
Net loss	$ (64,304)	$ (57,159)	[1],[2],[3]
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.29)	$ (0.28)	[1]
As Previously Reported
Revenue:
Product		$ 138,425
Support subscription		44,206
Total revenue		182,631
Gross profit		119,083
Sales and marketing		96,964
Total operating expenses		182,488
Loss from operations		(63,405)
Loss before provision for income taxes		(61,410)
Net loss		$ (62,374)
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)		$ (0.30)
Adjustment | Accounting Standards Update 2014-09
Revenue:
Product		$ 4,425
Support subscription		(4,411)
Total revenue		14
Gross profit		14
Sales and marketing		(5,201)
Total operating expenses		(5,201)
Loss from operations		5,215
Loss before provision for income taxes		5,215
Net loss		$ 5,215
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)		$ 0.02

[1] * Prior period information has been adjusted to reflect the adoption impact of ASC 606, which we adopted on February 1, 2018.

[2] * Prior period information has been adjusted to reflect the adoption impact of ASC 606 and ASU 2016-18, which we adopted on February 1, 2018

[3] * Prior period information has been adjusted to reflect the adoption impact of ASC 606, which we adopted on February 1, 2018.