Fair Value of Assets and Liabilities (Details) - USD ($) $ in Thousands	Apr. 30, 2020	Jan. 31, 2020
Assets:
Included in cash and cash equivalents	$ 182,611	$ 127,917
Total marketable securities	62,832	116,833
Derivative assets	1,648	683
Total assets measured at fair value	247,091	245,433
Liabilities:
Derivative liabilities	1,353	342
Total liabilities measured at fair value	1,353	342
Level 1
Assets:
Included in cash and cash equivalents	154,531	92,272
Total marketable securities	0	0
Derivative assets	0	0
Total assets measured at fair value	154,531	92,272
Liabilities:
Derivative liabilities	0	0
Total liabilities measured at fair value	0	0
Level 2
Assets:
Included in cash and cash equivalents	28,080	35,645
Total marketable securities	62,832	116,833
Derivative assets	1,648	683
Total assets measured at fair value	92,560	153,161
Liabilities:
Derivative liabilities	1,353	342
Total liabilities measured at fair value	1,353	342
Level 3
Assets:
Included in cash and cash equivalents	0	0
Total marketable securities	0	0
Derivative assets	0	0
Total assets measured at fair value	0	0
Liabilities:
Derivative liabilities	0	0
Total liabilities measured at fair value	0	0
Corporate notes and bonds
Assets:
Total marketable securities	4,777	5,675
Corporate notes and bonds | Level 1
Assets:
Total marketable securities	0	0
Corporate notes and bonds | Level 2
Assets:
Total marketable securities	4,777	5,675
Corporate notes and bonds | Level 3
Assets:
Total marketable securities	0	0
Commercial paper
Assets:
Total marketable securities	6,750	13,712
Commercial paper | Level 1
Assets:
Total marketable securities	0	0
Commercial paper | Level 2
Assets:
Total marketable securities	6,750	13,712
Commercial paper | Level 3
Assets:
Total marketable securities	0	0
U.S. government and agency securities
Assets:
Total marketable securities	51,305	97,446
U.S. government and agency securities | Level 1
Assets:
Total marketable securities	0	0
U.S. government and agency securities | Level 2
Assets:
Total marketable securities	51,305	97,446
U.S. government and agency securities | Level 3
Assets:
Total marketable securities	0	0
Money market funds
Assets:
Included in cash and cash equivalents	154,531	92,272
Money market funds | Level 1
Assets:
Included in cash and cash equivalents	154,531	92,272
Money market funds | Level 2
Assets:
Included in cash and cash equivalents	0	0
Money market funds | Level 3
Assets:
Included in cash and cash equivalents	0	0
Commercial paper
Assets:
Included in cash and cash equivalents	18,080	17,667
Commercial paper | Level 1
Assets:
Included in cash and cash equivalents	0	0
Commercial paper | Level 2
Assets:
Included in cash and cash equivalents	18,080	17,667
Commercial paper | Level 3
Assets:
Included in cash and cash equivalents	0	0
U.S. government and agency securities
Assets:
Included in cash and cash equivalents	10,000	17,978
U.S. government and agency securities | Level 1
Assets:
Included in cash and cash equivalents	0	0
U.S. government and agency securities | Level 2
Assets:
Included in cash and cash equivalents	10,000	17,978
U.S. government and agency securities | Level 3
Assets:
Included in cash and cash equivalents	$ 0	$ 0