Borrowings - Additional Information (Details)							1 Months Ended		3 Months Ended		9 Months Ended
	Aug. 14, 2019 USD ($)	Mar. 22, 2019 USD ($) $ / shares shares	Sep. 20, 2018 USD ($) $ / shares shares	Aug. 20, 2018 USD ($)	May 31, 2018 USD ($)	Jun. 29, 2017 USD ($) NumberofTime	Jun. 30, 2017 USD ($) $ / shares shares	Sep. 30, 2014 USD ($) $ / shares shares	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2019 USD ($)	Jun. 20, 2019 shares	Dec. 31, 2018 USD ($)	Oct. 03, 2014 USD ($)
Debt Disclosure [Line Items]
Line of credit outstanding															$ 5,000,000
Warrant issued to purchase stock | shares														188,643
Loss on debt extinguishment									$ (1,704,000)	$ (1,336,000)	$ (1,704,000)	$ (4,658,000)
Convertible Notes
Debt Disclosure [Line Items]
Loss on debt extinguishment				$ (800,000)
Debt instrument, face value						$ 12,200,000
Debt instrument, interest rate						8.00%
Debt instrument, maturity date						Jun. 28, 2018
Debt instrument, convertible, threshold of proceeds from equity financing, qualified financing						$ 10,000,000
Debt instrument, convertible, conversion price. number of times multiplied on qualified financing | NumberofTime						0.8
Debt instrument, percentage of outstanding principal amount to be repaid in cash in change of control						150.00%
Estimated fair value of compound derivative instrument						$ 500,000
Debt instrument, carrying value, reduction accretion period, based on effective interest method						1 year
Debt instrument, effective interest rate						12.69%
Debt instrument, extended maturity date				Sep. 20, 2018
Conversion of redeemable convertible preferred stock to common stock				$ 13,400,000
Convertible notes, equity component				$ 800,000
Debt instrument, carrying value, accretion period, based on effective interest method				1 month
Interest expense, debt										200,000		900,000
Revolving Loan
Debt Disclosure [Line Items]
Line of credit outstanding															5,000,000
Series C Redeemable Convertible Preferred Stock
Debt Disclosure [Line Items]
Conversion of redeemable convertible preferred stock to common stock			$ 13,400,000
Fair value of convertible notes, conversion of convertible securities | shares			1,667,997
Debt instrument, convertible, conversion price | $ / shares			$ 8.052
Series C Redeemable Convertible Preferred Stock | Revolving Loan
Debt Disclosure [Line Items]
Warrant issued to purchase stock | shares							62,096
Warrant exercise price per share | $ / shares							$ 8.052
Term Loan
Debt Disclosure [Line Items]
Estimated fair value of warrants								$ 100,000
Debt Instrument, term								4 years
Term Loan | Series B Redeemable Convertible Preferred Stock
Debt Disclosure [Line Items]
Warrant exercisable term								10 years
Warrant issued to purchase stock | shares								22,489
Warrant exercise price per share | $ / shares								$ 4.60
Convertible Notes
Debt Disclosure [Line Items]
Loss on debt extinguishment					$ (3,300,000)
Debt instrument, extended maturity date					Jun. 28, 2019
Conversion of redeemable convertible preferred stock to common stock					$ 13,100,000
Convertible notes, compound derivative asset					600,000
Convertible notes, equity component					$ 3,900,000
Debt instrument, carrying value, accretion period, based on effective interest method					1 year 1 month 6 days
Silicon Valley Bank | Term Loan
Debt Disclosure [Line Items]
Line of credit facility, maximum borrowing capacity								$ 3,000,000
Line of credit outstanding																$ 2,400,000
Line of credit facility, frequency of payments											12 interest-only payments, followed by 36 equal monthly installments of principal, plus interest
TriplePoint Capital LLC
Debt Disclosure [Line Items]
Line of credit facility, maximum borrowing capacity		$ 20,000,000
Line of credit outstanding													$ 20,000,000
Line of credit facility, frequency of payments											36 equal monthly payments of principal, plus accrued interest, from April 1, 2020 through March 1, 2023
Estimated fair value of warrants		$ 600,000
Line of credit facility interest rate											15.23%
Interest expense									$ 300,000		$ 1,000,000
Percentage of prepayment fee		1.00%
Percentage of principle payment amount		2.75%
Fees paid to lender		$ 300,000
Loss on debt extinguishment	$ (1,700,000)
TriplePoint Capital LLC | Common Stock
Debt Disclosure [Line Items]
Warrant issued to purchase stock | shares		65,502
Warrant exercise price per share | $ / shares		$ 9.16
TriplePoint Capital LLC | Maximum | Option One
Debt Disclosure [Line Items]
Line of credit outstanding		$ 15,000,000
TriplePoint Capital LLC | Minimum | Option Two
Debt Disclosure [Line Items]
Line of credit outstanding		$ 15,000,000
TriplePoint Capital LLC | Prime Rate | Option One
Debt Disclosure [Line Items]
Interest rate, prime rate plus		5.00%
TriplePoint Capital LLC | Prime Rate | Option Two
Debt Disclosure [Line Items]
Interest rate, prime rate plus		6.50%
TriplePoint Capital LLC | Revolving Loan
Debt Disclosure [Line Items]
Line of credit facility, maximum borrowing capacity							$ 10,000,000
Line of credit outstanding															5,000,000
Estimated fair value of warrants							$ 100,000
Debt Instrument, term							1 year 6 months
Line of credit facility interest rate							5.50%				19.22%
Line of credit facility maturity date											Dec. 31, 2018
Line of credit facility extended maturity date											Mar. 22, 2019
Line of credit facility, amount available to borrow															5,000,000
Interest expense										$ 200,000		$ 700,000
Accrued interest, related with accretion															$ 200,000
Repayments of amount outstanding		$ 5,300,000
TriplePoint Capital LLC | Revolving Loan | Prime Rate
Debt Disclosure [Line Items]
Interest rate, prime rate plus							6.75%
TriplePoint Capital LLC | Series C Redeemable Convertible Preferred Stock | Revolving Loan
Debt Disclosure [Line Items]
Warrant issued to purchase stock | shares							62,096
Warrant exercise price per share | $ / shares							$ 8.052