Stock-Based Compensation (Narrative) (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance (in shares)	2.3
Time-vested restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years) for shares awarded	3 years
Performance-based shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years) for shares awarded	3 years
Award vesting period	3 years
Level of performance achieved based on shares awarded, minimum	0.00%
Level of performance achieved based on shares awarded, maximum	200.00%
Time-vested restricted stock and deferred stock \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years
Time-vested restricted stock and deferred stock \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	5 years
Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost	$ 62.0
Weighted average recognition period, in years	2 years 3 months 18 days
Aggregate market value of the shares released and issued on the vesting dates		$ 49.0

Percentage Of Shares Awarded Based On Market Performance Achieved Maximum

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Percentage Of Shares Awarded Based On Market Performance Achieved Minimum

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Aggregate number of common shares reserved for future issuance.

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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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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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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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