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Stock-Based Compensation - Additional Information (Details)			1 Months Ended	3 Months Ended		9 Months Ended
	Apr. 17, 2018 Installment shares	Nov. 29, 2017 shares	May 31, 2018 $ / shares shares	Sep. 30, 2019 USD ($) shares	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) $ / shares shares	Sep. 30, 2018 USD ($)	Jun. 30, 2019 USD ($)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Cash proceeds from stock options exercised \| $						$ 6,000
Recognized stock-based compensation expense \| $						$ 2,808,000	$ 2,212,000
Restricted stock award issued						0
Options Issued and Outstanding
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of options exercised						7,029
Cash proceeds from stock options exercised \| $						$ 6,000
Options Issued and Outstanding \| Employees and Directors
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Option granted						1,276,684
Weighted-average grant date fair value of options granted \| $ / shares						$ 6.69
Expense related to options granted \| $				$ 1,200,000	$ 600,000	$ 2,700,000	1,200,000
Unrecognized compensation expense \| $				12,500,000		$ 12,500,000
Unrecognized compensation expense, estimated weighted-average period for recognition						3 years
Options Issued and Outstanding \| Non-employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Option granted						9,840
Weighted-average grant date fair value of options granted \| $ / shares						$ 7.61
Expense related to options granted \| $				18,000	37,000	$ 66,000	64,000
Unrecognized compensation expense \| $				200,000		$ 200,000
Unrecognized compensation expense, estimated weighted-average period for recognition						2 years 4 months 20 days
Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares granted	2,000
Number of quarterly installment in which restriction lapse \| Installment	4
Recognized stock-based compensation expense \| $				0	11,000	$ 4,000	900,000
Unrecognized stock-based compensation expense \| $				$ 0		$ 0
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation expense, estimated weighted-average period for recognition				2 years 7 months 20 days
Shares granted						0
Recognized stock-based compensation expense \| $				$ 14,000	$ 14,000	$ 42,000	$ 20,000
Unrecognized stock-based compensation expense \| $								$ 100,000
Restricted Stock Units \| Non-employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares granted						0
Restricted Stock Units \| Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares granted			24,960	0
Weighted-average grant date fair value \| $ / shares			$ 9.03
2017 Stock Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares reserved for issuance		630,662		537,914		537,914
Number of additional shares reserved for issuance		1,866,009				630,662
2017 Stock Incentive Plan \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Terms of stock based options granted						10 years
2018 Stock Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of additional shares added on outstanding shares						4.00%
2018 Stock Incentive Plan \| Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares reserved for issuance				2,200,260		2,200,260
2018 Stock Incentive Plan \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares reserved for issuance				3,322,473		3,322,473
2018 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares reserved for issuance				275,030		275,030
Percentage of additional shares added on outstanding shares						1.00%
2018 Employee Stock Purchase Plan \| Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of additional shares reserved for issuance						543,926
2018 Employee Stock Purchase Plan \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of additional shares reserved for issuance						555,583