Stock-based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Stock-based compensation
Proceeds from issuances of common stock from employee stock purchase plans	$ 358	$ 357
Unrecognized compensation cost related to outstanding options	$ 63,922
Period over which unrecognized compensation cost is expected to be recognized as expense	2 years 10 months 24 days
Restricted stock units
Stock-based compensation
Vesting period (in years)	4 years
Weighted-average grant date fair value of shares granted	$ 24.43	$ 21.34
Total fair value of shares vested	$ 9,116	$ 4,204
Stock options
Stock-based compensation
Weighted-average grant date fair value per share of grants (in dollars per share)	$ 12.08	$ 12.86
Employee stock purchase plan
Stock-based compensation
Employee Stock Purchase Plan, Purchase Price Percentage	85.00%
Issuance for employee stock purchase plan, shares	24,630
Proceeds from issuances of common stock from employee stock purchase plans	$ 358
Total purchased proceeds	$ 72	$ 79

Employee Stock Purchase Plan, Compensation Expense

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Employee Stock Purchase Plan, Purchase Price Percentage

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- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued with market-based vesting conditions during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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

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

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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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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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

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