Summary of Business and Significant Accounting Policies - Additional Information (Details) $ / shares in Units, $ in Thousands				1 Months Ended		9 Months Ended	12 Months Ended
	Apr. 30, 2019 USD ($)	Apr. 23, 2019 USD ($) $ / shares shares	Apr. 18, 2019 USD ($) $ / shares shares	Jan. 31, 2019 USD ($) shares	Jan. 31, 2018	Oct. 31, 2019 USD ($)	Jan. 31, 2020 USD ($) vote	Jan. 31, 2019 USD ($)	Jan. 31, 2018 USD ($)	Feb. 01, 2019 USD ($)
Summary Of Business And Significant Accounting Policies [Line Items]
Stockholders' equity note, stock split, conversion ratio					4
Stockholders' equity note, stock split, conversion ratio, shares (in shares) | shares				4
Sales and marketing							$ 340,646	$ 185,821	$ 82,707
Proceeds from international employee stock sales to be remitted to employees and tax authorities						$ 48,500	48,547	0	0
Purchase of equity investment						$ 3,000	3,000	0	0
Equity investment				$ 0			3,000	0
Advertising expense							$ 42,000	36,100	17,100
Number of operating segments | vote							1
Operating lease, total ROU assets							$ 68,608
Operating lease, total liabilities							$ 72,467
Revenue from Contract with Customer | Professional Services Fees Concentration Risk
Summary Of Business And Significant Accounting Policies [Line Items]
Percentage of revenue							2.00%
Minimum
Summary Of Business And Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life							3 years
Maximum
Summary Of Business And Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life							5 years
Convertible Debt
Summary Of Business And Significant Accounting Policies [Line Items]
Share price per share (in dollars per share) | $ / shares		$ 36.00
Leasehold Improvements | Maximum
Summary Of Business And Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life							5 years
Software
Summary Of Business And Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life							3 years
Property, plant and equipment, additions							$ 3,100	2,500	$ 800
Accounting Standards Update 2016-02
Summary Of Business And Significant Accounting Policies [Line Items]
Operating lease, total ROU assets										$ 40,500
Operating lease, total liabilities										$ 43,000
Other Assets, Non-current
Summary Of Business And Significant Accounting Policies [Line Items]
Capitalized deferred offering costs within other assets, non-current				$ 2,400				$ 2,400
Class A Common Stock | Convertible Debt
Summary Of Business And Significant Accounting Policies [Line Items]
Share price per share (in dollars per share) | $ / shares		$ 36.00
Over-Allotment Option
Summary Of Business And Significant Accounting Policies [Line Items]
Deferred offering costs, reclassified to stockholders' equity	$ (6,400)
Over-Allotment Option | Class A Common Stock
Summary Of Business And Significant Accounting Policies [Line Items]
Shares issued (in shares) | shares		9,911,434	3,130,435
Shares issued, price per share (in dollars per share) | $ / shares		$ 36.00	$ 36.00
Net proceeds from shares issued		$ 340,800	$ 107,100
Initial public offering | Class A Common Stock
Summary Of Business And Significant Accounting Policies [Line Items]
Convertible securities converted to common stock (in shares) | shares		426,223
Initial public offering | Class B Common Stock
Summary Of Business And Significant Accounting Policies [Line Items]
Convertible securities converted to common stock (in shares) | shares		152,665,804
Private Placement | Class A Common Stock
Summary Of Business And Significant Accounting Policies [Line Items]
Shares issued (in shares) | shares		2,777,777
Share price per share (in dollars per share) | $ / shares		$ 36.00
Aggregate proceeds from shares issued		$ 100,000