Stock-Based Compensation and Other Employee Benefit Plans (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Stock-Based Compensation and Other Employee Benefit Plans [Line Items]
Stock-based compensation plans, number of shares available for future grant	3,666,000		3,666,000
Non-cash stock-based compensation expense	$ 6.1	$ 5.8	$ 11.6	$ 9.9
Stock-based compensation, income tax benefits	1.2	$ 1.4	2.3	2.2
Stock-based compensation, vested awards, net tax benefits (deficiencies)	$ 0.1		$ 0.1	$ (0.2)
Restricted Shares \| Restated 2013 Incentive Plan
Stock-Based Compensation and Other Employee Benefit Plans [Line Items]
Share-based compensation, number of shares authorized	1,150,000		1,150,000

Amount of net tax benefit (deficiency) from vesting of share-based payment awards.

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- Definition

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

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Amount of tax benefit for recognition of expense of award under share-based payment arrangement.

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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.

+ References

No definition available.

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

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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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