Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands	Apr. 30, 2020	Jan. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Aggregate Fair Value	$ 62,832	$ 116,833
Cash, Cash Equivalents and Marketable Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	245,418	244,728
Unrealized Gains	25	22
Unrealized Losses	0	0
Aggregate Fair Value	245,443	244,750
Cash and Cash Equivalents
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	182,611	127,917
Unrealized Gains	0	0
Unrealized Losses	0	0
Aggregate Fair Value	182,611	127,917
Marketable Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	62,807	116,811
Unrealized Gains	25	22
Unrealized Losses	0	0
Aggregate Fair Value	62,832	116,833
Money market funds \| Cash, Cash Equivalents and Marketable Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	154,531	92,272
Unrealized Gains	0	0
Unrealized Losses	0	0
Aggregate Fair Value	154,531	92,272
U.S. government and agency securities \| Cash, Cash Equivalents and Marketable Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	61,284	115,412
Unrealized Gains	21	13
Unrealized Losses	0	0
Aggregate Fair Value	61,305	115,425
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Aggregate Fair Value	6,750	13,712
Commercial paper \| Cash, Cash Equivalents and Marketable Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	24,830	31,379
Unrealized Gains	0	0
Unrealized Losses	0	0
Aggregate Fair Value	24,830	31,379
Corporate notes and bonds \| Cash, Cash Equivalents and Marketable Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	4,773	5,665
Unrealized Gains	4	9
Unrealized Losses	0	0
Aggregate Fair Value	$ 4,777	$ 5,674

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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