Pension and Other Post-Retirement Benefits (Details 8) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Fair value of pension plan assets
Assets	$ 409.1	$ 377.5
Fair Value, Inputs, Level 1 [Member]
Fair value of pension plan assets
Assets	11.3	11.8
Fair Value, Inputs, Level 2 [Member]
Fair value of pension plan assets
Assets	397.8	365.7
Fair Value, Inputs, Level 3 [Member]
Fair value of pension plan assets
Assets	0	0
Short-term investment funds [Member]
Fair value of pension plan assets
Assets	1.0	2.9
Short-term investment funds [Member] \| Fair Value, Inputs, Level 1 [Member]
Fair value of pension plan assets
Assets	1.0	2.9
Short-term investment funds [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair value of pension plan assets
Assets	0	0
Short-term investment funds [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair value of pension plan assets
Assets	0	0
Common stock [Member]
Fair value of pension plan assets
Assets	10.3	8.9
Common stock [Member] \| Fair Value, Inputs, Level 1 [Member]
Fair value of pension plan assets
Assets	10.3	8.9
Common stock [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair value of pension plan assets
Assets	0	0
Common stock [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair value of pension plan assets
Assets	0	0
Common stock collective funds [Member]
Fair value of pension plan assets
Assets	245.0	222.5
Common stock collective funds [Member] \| Fair Value, Inputs, Level 1 [Member]
Fair value of pension plan assets
Assets	0	0
Common stock collective funds [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair value of pension plan assets
Assets	245.0	222.5
Common stock collective funds [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair value of pension plan assets
Assets	0	0
Fixed income collective trust funds [Member]
Fair value of pension plan assets
Assets	131.2	125.3
Fixed income collective trust funds [Member] \| Fair Value, Inputs, Level 1 [Member]
Fair value of pension plan assets
Assets	0	0
Fixed income collective trust funds [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair value of pension plan assets
Assets	131.2	125.3
Fixed income collective trust funds [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair value of pension plan assets
Assets	0	0
Real estate investment funds [Member]
Fair value of pension plan assets
Assets	21.6	17.9
Real estate investment funds [Member] \| Fair Value, Inputs, Level 1 [Member]
Fair value of pension plan assets
Assets	0	0
Real estate investment funds [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair value of pension plan assets
Assets	21.6	17.9
Real estate investment funds [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair value of pension plan assets
Assets	$ 0	$ 0

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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