Stock-Based Compensation - Employee Stock Purchase Plan (Details) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	May 31, 2019 item shares	Jul. 31, 2019 USD ($)	Jul. 31, 2018 USD ($)	Jul. 31, 2019 USD ($)	Jul. 31, 2018 USD ($)	Jan. 31, 2019 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee payroll contributions accrued		$ 20,057		$ 20,057		$ 19,284
Stock-based compensation		29,859	$ 2,224	33,611	$ 3,943
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Threshold percentage of outstanding shares	1.00%
Offering period	24 months
Number of purchase periods | item	4
Duration of purchase periods	6 months
Percentage of eligible compensation	15.00%
Maximum number of shares each participant can purchase during purchase period | shares	2,500
Purchase price, threshold percentage of fair market value	85.00%
Employee payroll contributions accrued		2,500		2,500
Stock-based compensation		$ 2,300		$ 2,300
Class A common stock | Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of shares of common stock that may be issued | shares	3,500,000