Equity Awards (Details) - USD ($) $ 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]
Net cash proceeds related to stock options exercised	$ 1.2	$ (1.8)	$ 8.6
Aggregate intrinsic value of stock options exercised	2.0	17.4	11.3
Stock-based compensation cost which has not yet been recognized	$ 30.0
Stock-based compensation cost recognized period, in months	1 year 10 months 24 days
Restricted stock awarded subject to performance condition (in shares)	308,000
Tax windfall related to share-based payment arrangements	$ 2.8	$ 4.0	$ 3.5
2018 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum term of the awards granted under the plan	10 years
Additional shares authorized for grants (in shares)	700,000

Maximum term of the awards granted under the plan.

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- Definition

Proceeds from (Payments for) Stock Options Exercised, Net

+ References

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- Definition

Restricted stock awarded subject to performance condition.

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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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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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- Definition

Amount of tax benefit from exercise of option under share-based payment arrangement.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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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 additional shares authorized for issuance under share-based payment arrangement.

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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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