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Stockholders' Equity - The 2017 Plan, Additional Information (Details) - 2017 Plan - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	6 Months Ended
	Jan. 31, 2019	Jun. 30, 2019	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted (in shares)		117,200
Options granted, exercise price (in dollars per share)		$ 13.60
Compensation not yet recognized		$ 3.1
Options to purchase common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted (in shares)	117,200
Options granted, exercise price (in dollars per share)	$ 12.75	$ 14.62
Expiration period	10 years	10 years
Fair value of option granted	$ 1.4
Stock based compensation expense		$ 1.9	$ 2.6
Options to purchase common stock \| One year from date of grant
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage		25.00%
Options to purchase common stock \| Every month thereafter through the fourth anniversary of the grant date
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage		2.0833%