Stock Compensation Plans (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options outstanding (in shares)	0	0
Time-Based RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost	$ 37.0
Weighted average period to recognize unrecognized compensation cost	2 years 2 months 15 days
Performance-Based RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost	$ 22.1
Weighted average period to recognize unrecognized compensation cost	2 years 3 months 14 days
Performance-Based RSUs \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Potential for awards to vest (as a percent)	0.00%
Performance-Based RSUs \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Potential for awards to vest (as a percent)	200.00%
Performance-Based RSUs \| Cliff
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
RSUs \| Cliff
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years

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- Definition

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

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
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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.

+ References

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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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Number of options outstanding, including both vested and non-vested options.

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