Fair Value Measurements - Summary of Fair Value Hierarchy for Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands		Jul. 31, 2020	Jan. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities		$ 436,463	$ 499,160
Corporate notes and bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities		75,717	156,023
U.S. treasury securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities		341,679	307,195
U.S. agency obligations
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities		11,011
Asset backed securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities		5,023	15,518
Fair value measurements recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets		1,219,565	621,413
Total liabilities		56	12,500
Fair value measurements recurring | Certificates of deposit
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities		3,033	4,447
Fair value measurements recurring | Money market funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	[1]	783,087	120,242
Fair value measurements recurring | Corporate notes and bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	[1]		2,011
Marketable securities		75,717	156,023
Fair value measurements recurring | U.S. treasury securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities		341,679	307,195
Fair value measurements recurring | Commercial paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities			15,977
Fair value measurements recurring | U.S. agency obligations
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities		11,011
Fair value measurements recurring | Asset backed securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities		5,023	15,518
Fair value measurements recurring | Foreign currency forward contracts | Not designated as hedges
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative assets	[2]	15
Derivative liabilities	[2]	56
Fair value measurements recurring | Contingent consideration payable
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other liabilities			12,500
Fair value measurements recurring | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets		783,087	120,242
Fair value measurements recurring | Level 1 | Money market funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	[1]	783,087	120,242
Fair value measurements recurring | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets		436,478	501,171
Total liabilities		56
Fair value measurements recurring | Level 2 | Certificates of deposit
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities		3,033	4,447
Fair value measurements recurring | Level 2 | Corporate notes and bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	[1]		2,011
Marketable securities		75,717	156,023
Fair value measurements recurring | Level 2 | U.S. treasury securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities		341,679	307,195
Fair value measurements recurring | Level 2 | Commercial paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities			15,977
Fair value measurements recurring | Level 2 | U.S. agency obligations
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities		11,011
Fair value measurements recurring | Level 2 | Asset backed securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities		5,023	15,518
Fair value measurements recurring | Level 2 | Foreign currency forward contracts | Not designated as hedges
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative assets	[2]	15
Derivative liabilities	[2]	$ 56
Fair value measurements recurring | Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total liabilities			12,500
Fair value measurements recurring | Level 3 | Contingent consideration payable
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other liabilities			$ 12,500

[1] Included in cash and cash equivalents.

[2] The derivative assets and derivative liabilities are related to foreign currency forward contracts at a notional amount of $3.8 million, which were assumed from the Bellin acquisition completed in June 2020. The derivative assets were included in prepaid expenses and other current assets, and the derivative liabilities were included in the accrued expenses and other current liabilities on the Company’s condensed consolidated balance sheets at July 31, 2020. The foreign currency forward contracts were accounted for as an economic hedge and as a result the changes in the fair value of the derivative assets and liabilities were recognized in the Company’s condensed consolidated statements of operations. The changes in the fair value during the quarter ended July 31, 2020 were not material.