Fair Value Measurements - Schedule of Financial Assets at Fair Value (Details) - USD ($) $ in Thousands	Jul. 31, 2019	Jan. 31, 2019
Assets:
Total cash and cash equivalents	$ 14,018	$ 15,370
Total short-term investments	14,637	27,253
Commercial Paper
Assets:
Total short-term investments	5,926	8,253
U.S. Government Securities
Assets:
Total short-term investments	5,180	11,088
Corporate Debt Securities
Assets:
Total short-term investments	2,384	4,735
U.S. Agency Securities
Assets:
Total short-term investments		990
Asset-backed Securities
Assets:
Total short-term investments	1,147	2,187
Level 1
Assets:
Total short-term investments	5,180	11,088
Level 1 | U.S. Government Securities
Assets:
Total short-term investments	5,180	11,088
Level 2
Assets:
Total short-term investments	9,457	16,165
Level 2 | Commercial Paper
Assets:
Total short-term investments	5,926	8,253
Level 2 | Corporate Debt Securities
Assets:
Total short-term investments	2,384	4,735
Level 2 | U.S. Agency Securities
Assets:
Total short-term investments		990
Level 2 | Asset-backed Securities
Assets:
Total short-term investments	1,147	2,187
Cash Equivalents
Assets:
Total cash and cash equivalents	10,347	11,380
Cash Equivalents | Commercial Paper
Assets:
Total cash and cash equivalents	1,498	5,429
Cash Equivalents | U.S. Government Securities
Assets:
Total cash and cash equivalents	1,996
Cash Equivalents | Money Market Funds
Assets:
Total cash and cash equivalents	6,853	5,951
Cash Equivalents | Level 1
Assets:
Total cash and cash equivalents	8,849	5,951
Cash Equivalents | Level 1 | U.S. Government Securities
Assets:
Total cash and cash equivalents	1,996
Cash Equivalents | Level 1 | Money Market Funds
Assets:
Total cash and cash equivalents	6,853	5,951
Cash Equivalents | Level 2
Assets:
Total cash and cash equivalents	1,498	5,429
Cash Equivalents | Level 2 | Commercial Paper
Assets:
Total cash and cash equivalents	1,498	5,429
Cash
Assets:
Total cash and cash equivalents	$ 3,671	$ 3,990