Pension and Other Postretirement Benefit Plans - Recurring Fair Value Measures, Activity in Level 3 (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Pension [Member] | Private Equity Funds [Member]
Activity in Level 3 [Roll Forward]
Beginning Balance	$ 58.9	$ 69.0
Actual Return on Plan Assets	2.3	(9.7)
Purchases, sales, and settlements, net	(14.4)	(0.4)
Ending Balance	46.8	58.9
Pension [Member] | Real Estate [Member]
Activity in Level 3 [Roll Forward]
Beginning Balance	24.9	21.7
Actual Return on Plan Assets	2.1	3.4
Purchases, sales, and settlements, net	(0.5)	(0.2)
Ending Balance	26.5	24.9
Postretirement Health and Life [Member] | Private Equity Funds [Member]
Activity in Level 3 [Roll Forward]
Beginning Balance	13.5	14.0
Actual Return on Plan Assets	2.4	0.2
Purchases, sales, and settlements, net	(2.8)	(0.7)
Ending Balance	$ 13.1	$ 13.5