Number Of Consecutive Trading Days For Total Shareholder Return (TSR) Calculation

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- Definition

Share-Based Compensation Arrangement By Share-based Payment Award, Equity Instruments Other Than Options, Vested Target

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- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term for Expected Volatility Rate

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- Definition

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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- Definition

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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- Definition

Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

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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- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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- Definition

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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- Definition

Number of shares authorized for issuance under share-based payment arrangement.

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- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Percentage of vesting of award under share-based payment arrangement.

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- Definition

Expected term of 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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Number of new stock issued during the period.

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Stock Based Compensation - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested shares (in shares)	1,790,342	1,603,766	1,790,342	1,603,766	1,603,766	837,123
Unrecognized compensation cost	$ 5.7	$ 6.9	$ 5.7	$ 6.9
Unrecognized compensation cost, period for recognition			1 year 8 months 12 days
Fair value of vested shares			$ 2.5	$ 1.8
Shares vested (in shares)			621,438	287,611
PSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of vested shares			$ 3.7
Fair value, expected term			3 years
Fair value, expected term for volatility rate			3 years
Shares vested (in shares)			974,074
Vested shares target (in shares)	842,792		842,792
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested shares (in shares)	1,016,252	441,746	1,016,252	441,746	441,746	0
Fair value of vested shares			$ 0.5
Requisite service period			3 years
Shares vested (in shares)			147,254	0
2017 Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of shares that may be issued (in shares)	43,170,000		43,170,000
Shares available for grant (in shares)	31,486,637		31,486,637		5,540,536
2017 Incentive Plan \| Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued (in shares)			687,503		507,821
2017 Incentive Plan \| Employee
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued (in shares)			2,689,394
2017 Incentive Plan \| Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested shares (in shares)	1,790,342		1,790,342		1,603,766
Shares available for grant (in shares)					4,798,517
Shares issued (in shares)					1,881,380
Share-based compensation expense	$ 1.0	$ 1.0	$ 3.2	$ 2.8
2017 Incentive Plan \| PSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant (in shares)	6,168,886		6,168,886
Share-based compensation expense	$ 0.9	1.3	$ 3.9	3.7
Unrecognized compensation cost	$ 9.2	7.0	$ 9.2	7.0
Unrecognized compensation cost, period for recognition			1 year 10 months 24 days
Award vesting period			3 years		3 years
Number of consecutive trading days for Total Shareholder Return (TSR) calculation			30 days
2017 Incentive Plan \| PSUs \| Relative TSR Performance is Less Than the 30th Percentile
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage			0.00%
2017 Incentive Plan \| PSUs \| Relative TSR Performance is Equal to the 50th Percentile
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage			100.00%
2017 Incentive Plan \| RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant (in shares)	1,016,252		1,016,252		441,746
Share-based compensation expense	$ 0.4	0.2	$ 1.3	0.7
Unrecognized compensation cost	$ 3.2	$ 2.1	$ 3.2	$ 2.1
Unrecognized compensation cost, period for recognition			1 year 10 months 24 days
2010 Stock Incentive Plan \| Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested shares (in shares)	0		0