Pension and Other Postretirement Benefit Plans - Sensitivity of a One-Percentage-Point Change in Health Care Trend Rates (Details) (Postretirement Health and Life [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
Postretirement Health and Life [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Effect of One Percent Increase on Total of Postretirement Health and Life Service and Interest Cost	$ 1.5
Effect of One Percent Increase on Postretirement Health and Life Obligation	21.6
Effect of One Percent Decrease on Total of Postretirement Health and Life Service and Interest Cost	(1.2)
Effect of One Percent Decrease on Postretirement Health and Life Obligation	$ (17.7)