| **Share-Based Payments - Textual (Details) - USD ($) $ / shares in Units, $ in Millions**                                           | 12 Months Ended |
|-------------------------------------------------------------------------------------------------------------------------------------|-----------------|
||
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                  |            |   |   |
| Weighted-average fair value per share (in dollars per share)                                                                        | $ 11.55         | $ 15.11 | $ 11.41 |
| Unrecognized compensation cost                                                                                                      | $ 1.1           |   |   |
| Intrinsic value of stock options exercised                                                                                          | $ 9.1           | $ 4.2 | $ 2.4 |
| 2008 Amended and Restated Equity Incentive Plan [Member]                                                                            |            |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                  |            |   |   |
| Shares authorized for grant under the Plan (shares)                                                                                 | 9,000,000       | 9,000,000 | 9,000,000 |
| 2016 Omnibus Performance Incentive Plan [Member]                                                                                    |            |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                  |            |   |   |
| Shares authorized for grant under the Plan (shares)                                                                                 | 14,000,000      |   |   |
| Stock Options [Member]                                                                                                              |            |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                  |            |   |   |
| Expiration period                                                                                                                   | 10 years        |   |   |
| Vesting period                                                                                                                      | 3 years         |   |   |
| Share-based compensation expense                                                                                                    | $ 1.6           | $ 1.6 | $ 1.9 |
| Weighted-average recognition period for unrecognized compensation cost                                                              | 26 months       |   |   |
| Employment Based SARS [Member]                                                                                                      |            |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                  |            |   |   |
| Shares granted during the period (shares)                                                                                           | 122,976         |   |   |
| Stock Appreciation Rights (SARs) [Member]                                                                                           |            |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                  |            |   |   |
| Share-based compensation expense                                                                                                    | $ 5.8           | $ 3.5 |   |
| Weighted-average recognition period for unrecognized compensation cost                                                              | 63 months       |   |   |
| Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options | $ 11.4          |   |   |
| Weighted-average fair value per share of awards granted (in dollars per share)                                                      | $ 84.33         | $ 64.09 |   |
| Outstanding awards (shares)                                                                                                         | 252,100         |   |   |
| Performance and Employment Based SARS [Member]                                                                                      |            |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                  |            |   |   |
| Shares granted during the period (shares)                                                                                           | 129,124         |   |   |
| Restricted Stock [Member]                                                                                                           |            |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                  |            |   |   |
| Share-based compensation expense                                                                                                    | $ 18.7          | $ 19.5 | $ 20.8 |
| Weighted-average recognition period for unrecognized compensation cost                                                              | 21 months       |   |   |
| Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options | $ 18.6          |   |   |
| Weighted-average fair value per share of awards granted (in dollars per share)                                                      | $ 33.56         | $ 27.86 | $ 23.94 |
| Fair value of vested shares                                                                                                         | $ 24.3          | $ 41.0 | $ 25.9 |
| Awards issued during period (shares)                                                                                                | 542,000         |   |   |
| Non-employee Directors [Member] | Restricted Stock Units (RSUs) [Member]                                                            |            |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                  |            |   |   |
| Weighted-average fair value per share of awards granted (in dollars per share)                                                      | $ 40.75         | $ 42.46 | $ 33.02 |
| Outstanding awards (shares)                                                                                                         | 434,134         |   |   |
| Awards issued during period (shares)                                                                                                | 32,031          | 30,744 | 36,350 |
| Compensation expense recognized                                                                                                     | $ 1.3           | $ 1.3 | $ 1.2 |
| Unrecognized compensation cost                                                                                                      | $ 0.0           |   |   |
| Non-employee Directors [Member] | Dividend Equivalent, RSU [Member]                                                                 |            |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                  |            |   |   |
| Awards issued during period (shares)                                                                                                | 10,248          | 7,645 | 8,149 |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                         |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Share-based Goods and Non-employee Services Transaction, Compensation Cost Not Yet Recognized, Share-based Awards Other Than Options
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| - Definition
Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.
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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.
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| - Definition
Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.
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Unrecognized cost of unvested options awarded to employees as compensation.
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| - Definition
Fair value of share-based compensation granted to nonemployees as payment for services rendered or acknowledged claims.
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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.
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| - Definition
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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| - Definition
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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| - Definition
Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.
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| - Definition
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
Net number of non-option equity instruments granted to participants.
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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Number of equity instruments other than options outstanding, including both vested and non-vested instruments.
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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).
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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
Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.
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