Pension and Other Post-retirement Benefits Narrative (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Amortization period for pension plan actuarial gains (losses) (in years)	20 years
Pension plan required minimum contributions, 2015	$ 13.3
Pension plan required minimum contributions, 2016	14.3
Pension plan required minimum contributions, 2017	15.3
Pension plan required minimum contributions, 2018	17.0
Pension plan required minimum contributions, 2019	18.3
Pension plan required minimum contributions, thereafter	56.4
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Aggregate expense of other postretirement benefit plans	$ 0.5	$ 0.4