Stockholders' Equity - The 2017 Plan, Additional Information (Details) - 2017 Plan - USD ($) $ / shares in Units, $ in Millions	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted (in shares)	184,700
Options granted, exercise price (in dollars per share)	$ 13.88
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)	184,700
Expiration period	10 years
Award vesting period	4 years
Fair value of option granted	$ 2.2
Stock based compensation expense	$ 2.4	$ 3.9
Options to Purchase Common Stock \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted, exercise price (in dollars per share)	$ 11.26
Options to Purchase Common Stock \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted, exercise price (in dollars per share)	$ 14.62
Options to Purchase Common Stock \| One Year from Date of Grant
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	1 year
Options to Purchase Common Stock \| One Year Anniversary of the Grant Date
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	25.00%
Options to Purchase Common Stock \| Every Month Thereafter Through he Fourth Anniversary of the Grant Date
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	2.0833%

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Amount of cost to be recognized for option under share-based payment arrangement.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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