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- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Payout Potential Cap

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- Definition

Share based compensation arrangement by share based payment award options exercisable rate.

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- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Payout Potential Range

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- Definition

weighted average of shares for total future compensation cost related to unvested share-based awards

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- Definition

weighted average period for unvested share-based RSUs to be recognized

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- Definition

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

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- Definition

Amount of cost to be recognized for nonvested award under share-based payment arrangement. Excludes share and unit options.

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- Definition

Amount of cost to be recognized for option under share-based payment arrangement.

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- Definition

The aggregate cash inflow comprised of the amount received from (a) employees to acquire the entity's shares under incentive awards, including stock option exercises and restricted stock arrangements, and (b) the excess tax benefit arising from such transactions.

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Amount of cash inflow from exercise of option 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.

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- Definition

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

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- Definition

Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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- Definition

Amount by which current fair value of underlying stock exceeds exercise price of fully vested and expected to vest exercisable or convertible options. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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- Definition

Fair value of options vested. Excludes equity instruments other than options, for example, but not limited to, share units, stock appreciation rights, restricted stock.

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Stock-Based Compensation Plans (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average fair value of options granted during period	$ 15.18	$ 15.79	$ 17.79
Fair value of shares vested	$ 6.2	$ 6.3	$ 6.5
Total intrinsic value of options exercised	4.1	6.8	17.6
Cash received from options exercised	5.1	2.9	16.1
Proceeds and Excess Tax Benefit from Share-based Compensation	0.6	3.8
Aggregate intrinsic value of exercisable options	29.5	39.4	16.7
Share-based Payment Arrangement, Nonvested Award, Option, Cost Not yet Recognized, Amount	$ 11.9
weighted average of shares for total future compensation cost related to unvested share-based awards	2 years 1 month 2 days
Share-based compensation expense recognized for restricted stock awards	$ 6.6	6.0	5.9
Share-based Payment Arrangement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash received from options exercised	$ 8.9	11.4	24.2
Share-based Payment Arrangement [Member] \| Options Exercisable After First Year [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercisable rate	25.00%
Share-based Payment Arrangement [Member] \| Options Exercisable After Second Year [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercisable rate	50.00%
Share-based Payment Arrangement [Member] \| Options Exercisable After Third Year [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercisable rate	75.00%
Share-based Payment Arrangement [Member] \| Options Exercisable After Fourth Year [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercisable rate	100.00%
Restricted Stock And Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting payout cap	100.00%
Period of time to measure Company total shareholder return and apply vesting payout cap (in years)	3 years
Share-based compensation expense recognized for restricted stock awards	$ 15.7	$ 16.3	$ 15.7
Share-based Payment Arrangement, Nonvested Award, Excluding Option, Cost Not yet Recognized, Amount	$ 23.8
weighted average period for unvested share-based RSUs to be recognized	1 year 10 months 13 days
Restricted Stock And Restricted Stock Units [Member] \| Options Exercisable After First Year [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercisable rate	25.00%
Restricted Stock And Restricted Stock Units [Member] \| Options Exercisable After Second Year [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercisable rate	50.00%
Restricted Stock And Restricted Stock Units [Member] \| Options Exercisable After Third Year [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercisable rate	75.00%
Restricted Stock And Restricted Stock Units [Member] \| Options Exercisable After Fourth Year [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercisable rate	100.00%
Minimum [Member] \| Restricted Stock And Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting payout potential range	0.00%
Maximum [Member] \| Restricted Stock And Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting payout potential range	200.00%
2013 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)	9,500,000
2018 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)	6,500,000