Components of Net Periodic Benefit Cost (Details) (Pension Benefits, USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Pension Benefits
Components of Net Periodic Benefit Cost
Service cost - benefits earned during the period	$ 3.7	$ 3.4	$ 7.3	$ 6.8
Interest cost on projected benefit obligation	8.5	8.8	17.0	17.7
Expected return on plan assets	(10.9)	(10.1)	(21.8)	(20.2)
Amortization of unrecognized transition obligation		0.1	0.1	0.1
Amortization of prior service cost	0.4	0.5	0.8	1.1
Recognized actuarial net (gain) or loss	7.0	5.9	14.1	11.7
Settlement loss (gain)		(2.5)	3.1	(2.5)
Net periodic benefit (income) cost	8.7	6.1	20.6	14.7
Defined contribution benefits plans	$ 5.5	$ 4.8	$ 10.8	$ 9.9

The amount of gains or losses recognized in net periodic benefit cost.

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The amount of the prior service cost or credit recognized in net periodic benefit cost relating to benefit changes attributable to plan participants' prior service pursuant to a plan amendment or a plan initiation.

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The amount of the transition obligation or asset recognized in net periodic benefit cost.

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An amount calculated as a basis for determining the extent of delayed recognition of the effects of changes in the fair value of assets. The expected return on plan assets is determined based on the expected long-term rate of return on plan assets and the market-related value of plan assets.

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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 total amount of net periodic benefit cost for defined benefit plans for the period. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) due to settlements or curtailments.

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The aggregate amount of net gain (loss) recognized in net periodic benefit cost due to settlements and curtailments. Curtailments result from an event that significantly reduces the expected years of future service of present employees or eliminates for a significant number of employees the accrual of defined benefits for some or all of their future services. Settlements result from an irrevocable action that relieves the employer (or the plan) of primary responsibility for a benefit obligation and eliminates significant risks related to the obligation and the assets used to effect the settlement. Examples of transactions that constitute a settlement include (a) making lump-sum cash payments to plan participants in exchange for their rights to receive specified benefits and (b) purchasing nonparticipating annuity contracts to cover vested benefits.

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- Definition

The actuarial present value of benefits attributed by the pension benefit formula to services rendered by employees during the period. The portion of the expected postretirement benefit obligation attributed to employee service during the period. The service cost component is a portion of the benefit obligation and is unaffected by the funded status of the plan.

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-Glossary Service Cost (Component of Net Periodic Pension Cost)

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The amount of the cost recognized during the period for defined contribution plans.

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