Subsequent Events - Additional Information (Details) - USD ($)			1 Months Ended				2 Months Ended	3 Months Ended				12 Months Ended
	Apr. 13, 2018	Jan. 31, 2018	Apr. 30, 2018	Mar. 31, 2018	Feb. 28, 2018	Sep. 30, 2017	Mar. 31, 2018	Jan. 31, 2019	Oct. 31, 2018	Jul. 31, 2018	Apr. 30, 2018	Jan. 31, 2018	Jan. 31, 2017	Jul. 31, 2017	Jun. 30, 2017	May 31, 2017
Subsequent Event [Line Items]
Aggregate principal amount		$ 68,962,000										$ 68,962,000
Interest rate, percentage		1.50%										1.50%
Restructuring charges												$ 899,000
Line of credit facility maximum borrowing capacity		$ 50,000,000										50,000,000
Line of credit facility, outstanding borrowings		$ 50,000,000										$ 50,000,000
Debt instrument, covenant description												Based on the Company’s assessment, it is probable that it will be unable to comply with its financial covenants through January 31, 2019, and it may fail to comply with certain financial covenants as early as May 31, 2018, and as such it has classified all outstanding debt balances as of January 31, 2018 as a current liability
Line of credit facility, extended maturity month and year												2020-08
Shares reserved for future issuance		13,978,102										13,978,102	16,490,604
Number of shares underlying outstanding, Options granted												1,580,416
RSUs
Subsequent Event [Line Items]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period												7,157,672	319,885
Minimum
Subsequent Event [Line Items]
Board of directors approved percentage of restructuring and reduction in force plan						10.00%
Amount to be paid on or before the maturity date												$ 20,000,000
Note Purchase Agreement | Convertible Promissory Notes
Subsequent Event [Line Items]
Notes issued		$ 0
Line of credit facility maximum borrowing capacity																$ 25,000,000
SVB Credit Facility | Revolving Line of Credit
Subsequent Event [Line Items]
Line of credit facility maximum borrowing capacity		20,000,000										20,000,000
Line of credit facility, outstanding borrowings		$ 19,000,000										$ 19,000,000
Line of credit facility expiration period												2018-05
SVB Credit Facility | Scenario Forecast | Revolving Line of Credit | Financial Covenants
Subsequent Event [Line Items]
Revenues								$ 29,400,000	$ 26,300,000	$ 23,400,000	$ 20,500,000
Common Stock | IPO
Subsequent Event [Line Items]
Shares price		$ 7.00										$ 7.00		$ 7.00
Common Stock | IPO | Note Purchase Agreement | Convertible Promissory Notes
Subsequent Event [Line Items]
Shares price															$ 7.00
Subsequent Event
Subsequent Event [Line Items]
Lease anticipated termination date					Apr. 30, 2018
Expected lease termination costs, net					$ 3,700,000
Write-off of net leasehold costs					2,500,000
Contract termination costs					1,800,000
Recovery of deferred rental expenses, partly offset					600,000
Cash expenditures related to contract termination costs					$ 1,800,000
Board of directors approved percentage of restructuring and reduction in force plan				20.00%
Restructuring activities, completion date				Apr. 30, 2018
Line of credit, amended and modified agreement date				May 14, 2013
Subsequent Event | Inducement Plan
Subsequent Event [Line Items]
Shares reserved for future issuance			1,700,000								1,700,000
Number of shares underlying outstanding, Options granted	1,700,000
Share-based compensation arrangement by share-based payment award, equity instruments options, grant date fair value	$ 1,400,000
Subsequent Event | RSUs | 2017 Plan
Subsequent Event [Line Items]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period				2,846,025
Share-based compensation arrangement by share-based payment award equity instruments other than options grant date fair value				$ 12,600,000
Subsequent Event | Prime Rate
Subsequent Event [Line Items]
Variable rate				1.85%
Subsequent Event | Minimum
Subsequent Event [Line Items]
Cash expenditures related to restructuring including severance and termination costs				$ 3,000,000
Subsequent Event | Minimum | Severance Costs
Subsequent Event [Line Items]
Restructuring charges				2,500,000
Subsequent Event | Maximum
Subsequent Event [Line Items]
Cash expenditures related to restructuring including severance and termination costs				4,000,000
Subsequent Event | Maximum | Severance Costs
Subsequent Event [Line Items]
Restructuring charges				3,500,000
Subsequent Event | Note Purchase Agreement | Convertible Promissory Notes
Subsequent Event [Line Items]
Notes issued							$ 25,000,000
Aggregate principal amount				$ 25,000,000			$ 25,000,000
Interest rate, percentage				8.00%			8.00%
Maturity period							18 months
Debt instrument, description							If the Notes remain outstanding on or after December 1, 2019, at the Company’s election, pursuant to the approval of a majority of the members of the Company’s board of directors, the Notes will convert into shares of the Company’s common stock at the IPO price of $7.00 per share, provided that any Notes issued to entities affiliated with one of the Company’s existing stockholders that is a party to the Note Purchase Agreement will be converted at the average price of the Company’s common stock on the NASDAQ Stock Market over the 30-day period preceding the conversion.
Line of credit facility, maturity month and year							2019-08
Subsequent Event | SVB Credit Facility | Revolving Line of Credit
Subsequent Event [Line Items]
Line of credit facility maximum borrowing capacity			$ 12,500,000								$ 12,500,000
Subsequent Event | SVB Credit Facility | Revolving Line of Credit | Financial Covenants
Subsequent Event [Line Items]
Debt instrument, covenant description			The Company’s revolving line of credit with SVB contains certain financial covenants, including a covenant that it achieve total revenues of at least $20.5 million, $23.4 million, $26.3 million and $29.4 million for the fiscal quarters ending April 30, 2018, July 31, 2018, October 31, 2018 and January 31, 2019, respectively, and a covenant that the it maintain a minimum level of cash and availability under the SVB line of credit of at least $15.0 million through July 31, 2018 and at least $10.0 million thereafter. The Company may also be required to pay a fee to SVB upon a change of control.
Subsequent Event | SVB Credit Facility | Minimum | Revolving Line of Credit | Financial Covenants
Subsequent Event [Line Items]
Minimum level of cash and availability under line of credit through July 31,2018			$ 15,000,000								15,000,000
Minimum level of cash and availability under line of credit, thereafter			10,000,000								10,000,000
Subsequent Event | Non-formula SVB Credit Facility | Revolving Line of Credit
Subsequent Event [Line Items]
Line of credit facility, outstanding borrowings			$ 5,000,000								5,000,000
Line of credit facility expiration period			2018-05
Subsequent Event | TriplePoint Credit Facility
Subsequent Event [Line Items]
Line of credit facility, outstanding borrowings			$ 50,000,000								50,000,000
Line of credit facility, maturity month and year			2019-08
Line of credit facility, extended maturity month and year			2021-02
Subsequent Event | TriplePoint Credit Facility | 10.5% Line of Credit Facility Due in August 2019
Subsequent Event [Line Items]
Line of credit facility, outstanding borrowings			$ 15,000,000								$ 15,000,000
Line of credit facility, maturity month and year			2019-08
Credit facility, bears interest rate			10.50%								10.50%
Subsequent Event | TriplePoint Credit Facility | 12.75% Line of Credit Facility Due in August 2019
Subsequent Event [Line Items]
Line of credit facility, outstanding borrowings			$ 35,000,000								$ 35,000,000
Credit facility, bears interest rate			12.75%								12.75%
Subsequent Event | TriplePoint Credit Facility | Minimum
Subsequent Event [Line Items]
Amount to be paid on or before the maturity date			$ 25,000,000
205 Ravendale Drive, Mountain View, California | Subsequent Event
Subsequent Event [Line Items]
Lease termination, month and year					2018-02