Segment Information - Schedule of Revenue by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jul. 31, 2018	Jul. 31, 2017		Jul. 31, 2018	Jul. 31, 2017
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenue	$ 308,884	$ 224,670	[1]	$ 564,829	$ 407,315
United States
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenue	229,760	165,620		414,678	312,125
Rest of the world
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenue	$ 79,124	$ 59,050		$ 150,151	$ 95,190

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