| **Stock-based Compensation Plans - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions**                                              | 12 Months Ended         |
|----------------------------------------------------------------------------------------------------------------------------------------------------|-------------------------|
||
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                                 |                    |   |   |
| Expected Dividend Rate                                                                                                                             | 0.00%                   |   |   |
| Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value               | $ 13.70                 | $ 13.81 | $ 14.01 |
| Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value                                   | $ 0.0                   | $ 12.0 | $ 4.0 |
| Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value                                                    | $ 10.53                 | $ 14.12 | $ 14.01 |
| Stock-based compensation                                                                                                                           | $ 9.0                   | $ 16.0 | $ 24.0 |
| Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized                                                  | $ 35.0                  |   |   |
| Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition                          | 1 year 3 months 18 days |   |   |
| Employee Service Share-based Compensation, Cash Received from Exercise of Stock Options                                                            | $ 1.0                   | 19.0 | 12.0 |
| Deferred Share Units [Member]                                                                                                                      |                    |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                                 |                    |   |   |
| Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Outstanding Number                       | 2,365                   |   |   |
| Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested, Number Of Common Stock Delivered | 1                       |   |   |
| Share-based Compensation Arrangement by Share-based Payment Award, Accelerated Vesting, Delivery Period of Shares                                  | 10 days                 |   |   |
| Deferred Fee Plan [Member]                                                                                                                         |                    |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                                 |                    |   |   |
| Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Outstanding Number                       | 45,724                  |   |   |
| Employee Stock Option [Member]                                                                                                                     |                    |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                                 |                    |   |   |
| Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period                                                            | 3 years                 |   |   |
| Restricted Stock [Member]                                                                                                                          |                    |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                                 |                    |   |   |
| Share-based Compensation Arrangement By Share-based Payment Award, Equity Instruments Other than Options, Aggregate Grant Date Fair Value          | $ 1.1                   | $ 0.1 | $ 0.1 |
| Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period                                                            | 3 years                 |   |   |
| Equity Instruments Other than Options, Grants in Period                                                                                            | 2,000                   | 4,000 | 2,000 |
| Equity Instruments Other than Options, Vested in Period                                                                                            | 43,000                  | 4,000 | 2,000 |
| Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value                                                    | $ 29.50                 | $ 33.70 | $ 34.19 |
| Restricted Stock Units (RSUs) [Member]                                                                                                             |                    |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                                 |                    |   |   |
| Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other Than Options, Settlement by Cash or Shares, Number     | 10,000                  |   |   |
| Share-based Compensation Arrangement By Share-based Payment Award, Equity Instruments Other than Options, Aggregate Grant Date Fair Value          | $ 10.0                  | $ 9.0 | $ 10.0 |
| Performance-based Stock Options [Member]                                                                                                           |                    |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                                 |                    |   |   |
| Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period                                                               | 7 years                 |   |   |
| Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period                                                            | 3 years                 |   |   |
| Equity Instruments Other than Options, Grants in Period                                                                                            | 729,000                 | 651,000 | 299,000 |
| Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value                                                    | $ 27.61                 | $ 35.83 | $ 34.47 |
| Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other Than Options, Exercisable, Number                      | 0                       | 0 | 0 |
| Share-based Compensation Arrangement by Share-based Payment Award, Extended Award Vesting Period                                                   | 5 years                 |   |   |
| Premium Share Units [Member]                                                                                                                       |                    |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                                 |                    |   |   |
| Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Outstanding Number                       | 46,631                  |   |   |
| Cash-Settled Restricted Stock Units [Member]                                                                                                       |                    |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                                 |                    |   |   |
| Equity Instruments Other than Options, Grants in Period                                                                                            | 280,000                 | 470,000 | 3,000 |
| Equity Instruments Other than Options, Vested in Period                                                                                            | 190,000                 | 124,000 | 215,000 |
| Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value                                                    | $ 27.67                 | $ 32.44 | $ 27.24 |
| Employee Service Share-based Compensation, Cash Flow Effect, Cash Used to Settle Awards                                                            | $ 6.0                   | $ 5.0 | $ 5.0 |
| Plan 2013 [Member]                                                                                                                                 |                    |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                                 |                    |   |   |
| Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized                                                     |                    |   | 3,665,500 |
| Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant                                            | 1,589,356               |   |   |
| Stock Options Granted Prior to December 2009 [Member] | Employee Stock Option [Member]                                                             |                    |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                                 |                    |   |   |
| Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period                                                               | 10 years                |   |   |
| Stock Options Granted After December 2009 [Member] | Employee Stock Option [Member]                                                                |                    |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                                                 |                    |   |   |
| Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period                                                               | 7 years                 |   |   |

| X                                                                                                                                                                                                                                                                                                                                                                                                                      |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
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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
Aggregate cash paid by the entity during the period to settle equity instruments granted under equity-based payment arrangements.
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| - Definition
Aggregate proceeds received by the entity during the annual period from exercises of stock or unit options and conversion of similar instruments granted under equity-based payment arrangements.
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| - Definition
Unrecognized cost of unvested share-based compensation awards.
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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
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
The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.
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| - Definition
The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.
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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
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
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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| - 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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