Stock-Based Compensation - Employee Stock Purchase Plan (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Jan. 01, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from stock issued in connection with the employee stock purchase plan	$ 13,040	$ 15,129
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance (in shares)	5,431,176		1,478,808
Common stock purchased (in shares)	667,719
Share price (in usd per share)	$ 19.53
Employee contributions	$ 2,700
Unrecognized stock-based compensation expense	$ 5,900
Remaining offering period	8 months 12 days

Aggregate number of common shares reserved for future issuance.

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Total of the carrying values as of the balance sheet date of obligations incurred through that date and payable for obligations related to services received from employees, such as accrued salaries and bonuses, payroll taxes and fringe benefits.

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of cash inflow from issuance of shares under share-based payment arrangement. Excludes option exercised.

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Number of shares issued during the period as a result of an employee stock purchase plan.

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