Significant Accounting Policies - Revenues by Geographic Area (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
Entity Wide Information Revenue From External Customer [Line Items]
Total revenues	$ 133,775	$ 83,678	$ 50,845
United States
Entity Wide Information Revenue From External Customer [Line Items]
Total revenues	90,449	60,411	38,091
Foreign Countries
Entity Wide Information Revenue From External Customer [Line Items]
Total revenues	$ 43,326	$ 23,267	$ 12,754