Share-Based Payments (Summary of the Restricted Stock Unit Transactions under Share-Based Payment Plans) (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash Incentive Plan [Member]
Weighted average remaining expense life	1 year 1 month 18 days
Share Based Compensation Liability Awards Amount Of Liability	$ 21.9
Cash incentive unit payments made	9.0	4.7	3.0
Restricted Stock Units (RSUs) [Member]
Unvested RSU awards at December 31, 2013	1,096,780
Granted in 2014, number of shares	374,963
Vested in 2014, number of shares	378,150
Forfeited in 2014, number of shares	16,583
Unvested RSU awards at Decemeber 31, 2014, number of shares	1,077,010	1,096,780
Unvested RSU awards at December 31, 2013, weighted average grant date fair value	$ 18.73
Granted in 2014, weighted average grant date fair value	$ 21.58	$ 21.03	$ 17.62
Vested in 2014, weighted average grant date value	$ 17.47
Forfeited in 2014, weighted average grant date fair value	$ 19.19
Unvested RSU awards at December 31, 2014, weighted average grant date fair value	$ 20.18	$ 18.73
Total unrecognized compensation cost related to unvested RSU awards	4.7
Weighted average remaining expense life	1 year 7 months 18 days
Dividend Equivalent Units [Member]
Total intrinsic value of shares vested	0.7	0.9	0.9
Restricted Stock Units [Member]
Total intrinsic value of shares vested	$ 8.5	$ 9.1	$ 8.4

The liability recorded in connection with our Cash Incentive Plan.

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Unrecognized cost of unvested share-based compensation awards.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (i)

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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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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(iv)(3)

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- Definition

Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

+ References

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-Subparagraph (c)(2)(iii)(3)

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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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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 non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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-Publisher FASB

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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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Amount of cash paid related to share-based compensation liabilities.

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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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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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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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