Segment Information - Revenue by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2019	Jul. 31, 2018
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenue	$ 396,327	$ 308,884	$ 723,027	$ 564,829
United States
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenue	294,596	229,760	523,535	414,678
Rest of the world
Revenues From External Customers And Long Lived Assets [Line Items]
Total revenue	$ 101,731	$ 79,124	$ 199,492	$ 150,151