Debt (Details) - USD ($)	Mar. 16, 2016	Jul. 31, 2018	Jan. 31, 2018
Line of Credit Facility [Line Items]
Long-term debt		$ 0	$ 0
Line of Credit | Silicon Valley Bank
Line of Credit Facility [Line Items]
Covenant terms, minimum adjusted quick ratio	1.25
Line of Credit | Silicon Valley Bank | Revolving Credit Line
Line of Credit Facility [Line Items]
Borrowing capacity	$ 15,000,000
Commitment fee, percentage	0.25%
Remaining borrowing capacity		$ 15,000,000
Line of Credit | Silicon Valley Bank | Letter of Credit
Line of Credit Facility [Line Items]
Borrowing capacity	$ 7,000,000
Commitment fee, percentage	1.75%
Line of Credit | Prime Rate | Silicon Valley Bank | Revolving Credit Line
Line of Credit Facility [Line Items]
Basis spread on variable rate	0.50%