Fair Value Measurement - Schedule of Financial Assets at Fair Value (Details) - USD ($) $ in Thousands	Oct. 31, 2017	Jan. 31, 2017
Assets:
Total cash and cash equivalents	$ 4,947	$ 3,990
Total short-term investments	48,574	49,211
Commercial Paper
Assets:
Total short-term investments	5,912	5,386
U.S. Agency Securities
Assets:
Total short-term investments	2,744	5,777
Corporate Debt Securities
Assets:
Total short-term investments	19,436	18,436
U.S. Government Securities
Assets:
Total short-term investments	19,602	17,798
Asset-backed Securities
Assets:
Total short-term investments	880	1,814
Level 1
Assets:
Total short-term investments	19,602	17,798
Level 1 | U.S. Government Securities
Assets:
Total short-term investments	19,602	17,798
Level 2
Assets:
Total short-term investments	28,972	31,413
Level 2 | Commercial Paper
Assets:
Total short-term investments	5,912	5,386
Level 2 | U.S. Agency Securities
Assets:
Total short-term investments	2,744	5,777
Level 2 | Corporate Debt Securities
Assets:
Total short-term investments	19,436	18,436
Level 2 | Asset-backed Securities
Assets:
Total short-term investments	880	1,814
Cash Equivalents
Assets:
Total cash and cash equivalents	1,957	951
Cash Equivalents | Commercial Paper
Assets:
Total cash and cash equivalents	1,398
Cash Equivalents | Money Market Funds
Assets:
Total cash and cash equivalents	559	951
Cash Equivalents | Level 1
Assets:
Total cash and cash equivalents	559	951
Cash Equivalents | Level 1 | Money Market Funds
Assets:
Total cash and cash equivalents	559	951
Cash Equivalents | Level 2
Assets:
Total cash and cash equivalents	1,398
Cash Equivalents | Level 2 | Commercial Paper
Assets:
Total cash and cash equivalents	1,398
Cash
Assets:
Total cash and cash equivalents	$ 2,990	$ 3,039