Share-Based Compensation and Stock Repurchases (Details) - USD ($) $ / shares in Units, $ in Millions	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018
Share-Based Compensation
Upon vesting, each restricted stock unit and performance share replaced with common stock	1.00%
Stock based compensation expense	$ 8.0	$ 10.4
Employee severance related costs	7.9
Forfeiture credit	$ 4.5
Common stock repurchased (in shares)	1,496,648	427,869
Common stock repurchased, value	$ 84.6	$ 25.2
Payment of income tax obligation on employee equity awards	$ 9.3	$ 13.6
Restricted stock units
Share-Based Compensation
Granted (in dollars per share)	$ 48.73
Restricted stock units \| Long Term Incentive Plan 2010
Share-Based Compensation
Granted (in shares)	104,120
Vesting period	3 years
Performance stock units \| Long Term Incentive Plan 2010
Share-Based Compensation
Granted (in shares)	87,864
Vesting period	3 years
Performance stock units \| Minimum \| Long Term Incentive Plan 2010
Share-Based Compensation
Percentage number of performance shares awarded	0.00%
Performance stock units \| Maximum \| Long Term Incentive Plan 2010
Share-Based Compensation
Percentage number of performance shares awarded	200.00%
Director
Share-Based Compensation
Granted (in shares)	18,576
Granted (in dollars per share)	$ 48.45

The amount of forfeiture credit.

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Represents severance cost gross.

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Upon vesting, each restricted stock unit and performance share replaced with common stock.

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- Definition

The number of performance shares awarded represented as a percentage of the original granted amount based on performance.

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

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Amount of cash outflow to satisfy grantee's tax withholding obligation for award under share-based payment arrangement.

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- Definition

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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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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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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Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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Equity impact of the value of stock that has been repurchased during the period and has not been retired and is not held in treasury. Some state laws may mandate the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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