Significant Customers and Geographic Information - Revenues by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2017	Oct. 31, 2016
Entity Wide Information Revenue From External Customer [Line Items]
Total revenues	$ 47,340	$ 35,442	$ 133,028	$ 95,757
United States
Entity Wide Information Revenue From External Customer [Line Items]
Total revenues	31,272	23,230	87,335	65,840
Foreign Countries
Entity Wide Information Revenue From External Customer [Line Items]
Total revenues	$ 16,068	$ 12,212	$ 45,693	$ 29,917