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

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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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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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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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Stock-Based Compensation - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 0.5	$ 0.7	$ 2.0	$ 2.0
Options to purchase common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options vesting period			4 years
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense	$ 7.1		$ 7.1
Unrecognized compensation expense, recognition term			3 years 3 months 18 days
Minimum \| Restricted Stock and Performance Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options vesting period			1 year
Maximum \| Restricted Stock and Performance Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options vesting period			4 years