Fair Value of Assets and Liabilities (Details) - USD ($) $ in Thousands	Jul. 31, 2020	Jan. 31, 2020
Assets:
Included in cash and cash equivalents	$ 127,130	$ 127,917
Total marketable securities	121,741	116,833
Derivative assets	453	683
Total assets measured at fair value	249,324	245,433
Liabilities:
Derivative liabilities	1,006	342
Total liabilities measured at fair value	1,006	342
Level 1
Assets:
Included in cash and cash equivalents	113,131	92,272
Total marketable securities	0	0
Derivative assets	0	0
Total assets measured at fair value	113,131	92,272
Liabilities:
Derivative liabilities	0	0
Total liabilities measured at fair value	0	0
Level 2
Assets:
Included in cash and cash equivalents	13,999	35,645
Total marketable securities	121,741	116,833
Derivative assets	453	683
Total assets measured at fair value	136,193	153,161
Liabilities:
Derivative liabilities	1,006	342
Total liabilities measured at fair value	1,006	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	0	5,674
Corporate notes and bonds | Level 1
Assets:
Total marketable securities	0	0
Corporate notes and bonds | Level 2
Assets:
Total marketable securities	0	5,674
Corporate notes and bonds | Level 3
Assets:
Total marketable securities	0	0
Commercial paper
Assets:
Total marketable securities	16,754	13,713
Commercial paper | Level 1
Assets:
Total marketable securities	0	0
Commercial paper | Level 2
Assets:
Total marketable securities	16,754	13,713
Commercial paper | Level 3
Assets:
Total marketable securities	0	0
U.S. government and agency securities
Assets:
Total marketable securities	104,987	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	104,987	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	113,131	92,272
Money market funds | Level 1
Assets:
Included in cash and cash equivalents	113,131	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	8,999	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	8,999	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	5,000	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	5,000	17,978
U.S. government and agency securities | Level 3
Assets:
Included in cash and cash equivalents	$ 0	$ 0