Benefit Plans (Obligations and Funded Status) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Change in Benefit Obligation [Roll Forward]
Benefit obligation	$ 98.7	$ 96.8
Interest cost	4.4	5.0	5.1
Benefits paid	(9.3)	(8.4)
Actuarial gain on obligation	3.4	18.4
Plan adjustments	0	(8.8)
Curtailments or settlements	0	(4.3)
Benefit obligation	97.2	98.7	96.8
Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets	0	0
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Accrued benefit cost	(97.2)	(98.7)	(96.8)
Accumulated other comprehensive income:
Prior service cost	7.3	8.5
Net amount recognized	$ (104.5)	$ (107.2)

Defined Benefit Plan, Amounts Recognized in Balance Sheet and Accumulated Other Comprehensive Income (Loss), after Tax

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Defined Benefit Plan, Curtailments or Settlements

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Amount related to after tax cost of benefit changes attributable to plan participants' prior service pursuant to a plan amendment or a plan initiation, which has not yet been recognized as components of net periodic benefit cost.

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- Definition

Amount of gain (loss) from a decision to temporarily deviate from the substantive plan, or from a change in benefit obligation or plan asset value from changes in actuarial assumptions, for example, but not limited to, interest, mortality, employee turnover or salary scale.

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- Definition

1) For defined benefit pension plans, the benefit obligation is the projected benefit obligation, which is the actuarial present value as of a date of all benefits attributed by the pension benefit formula to employee service rendered prior to that date. 2) For other postretirement defined benefit plans, the benefit obligation is the accumulated postretirement benefit obligation, which is the actuarial present value of benefits attributed to employee service rendered to a particular date.

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The amount of payments made for which participants are entitled under a pension plan, including pension benefits, death benefits, and benefits due on termination of employment. Also includes payments made under a postretirement benefit plan, including prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services. This item represents a periodic decrease to the plan obligations and a decrease to plan assets.

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-Glossary Postretirement Benefits

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- Definition

Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.

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- Definition

The increase in a defined benefit pension plan's projected benefit obligation or a defined benefit postretirement plan's accumulated postretirement benefit obligation due to the passage of time.

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The amount of increase or decrease due to a change in the terms of an existing plan or the initiation of a new plan. A plan amendment may increase or decrease benefits, including those attributed to years of service already rendered.

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