Information about Geographic Areas - Revenues by Geographic Area (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Jan. 31, 2018	Oct. 31, 2017	Jul. 31, 2017	Apr. 30, 2017	Jan. 31, 2017	Oct. 31, 2016	Jul. 31, 2016	Apr. 30, 2016	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Revenues by geography
Total revenues	$ 184,919	$ 176,149	$ 166,585	$ 157,918	$ 150,153	$ 142,779	$ 131,347	$ 119,764	$ 685,571	$ 544,043	$ 409,221
North America [Member]
Revenues by geography
Total revenues									376,538	297,014	225,483
Europe and other [Member]
Revenues by geography
Total revenues									202,411	160,666	111,923
Asia Pacific [Member]
Revenues by geography
Total revenues									$ 106,622	$ 86,363	$ 71,815