Accounting Standards and Significant Accounting Policies - Revenue by Geographical Area (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jul. 31, 2018	Jul. 31, 2017		Jul. 31, 2018	Jul. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue by geographical area	$ 94,586	$ 60,259	[1]	$ 178,207	$ 112,584	[1]
United States
Disaggregation of Revenue [Line Items]
Revenue by geographical area	79,499	50,972		150,757	95,943
International
Disaggregation of Revenue [Line Items]
Revenue by geographical area	$ 15,087	$ 9,287		$ 27,450	$ 16,641

[1] See Note 2 for a summary of adjustments.