Pension and Postretirement Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Capitalized portion of defined benefit contribution percent			10.00%	10.00%
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Curtailment gain	$ (0.6)	$ 0	$ (0.6)	$ 0
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year					44
Pension and Other Postretirement Benefit Contributions			8.9
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	0.8	0.7	1.4	1.3
Interest cost on projected benefit obligation	4.2	4.6	9.4	10.7
Expected return on plan assets	(6.8)	(6.1)	(12.9)	(13.0)
Curtailment gain	(0.6)	0	(0.6)	0
Amortization of:
Prior service cost (benefit)	0.1	0.1	0.1	0.1
Actuarial loss	5.0	5.8	11.0	9.7
Total amortization	5.1	5.9	11.1	9.8
Benefit costs	2.7	5.1	8.4	8.8
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year					21
Pension and Other Postretirement Benefit Contributions			9.1
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	0.1	0.1	0.2	0.2
Interest cost on projected benefit obligation	0.7	1.2	2.0	2.8
Expected return on plan assets	0	0	0	0
Curtailment gain	0	0	0	0
Amortization of:
Prior service cost (benefit)	(3.3)	(3.3)	(6.5)	(6.6)
Actuarial loss	1.3	1.8	2.9	3.4
Total amortization	(2.0)	(1.5)	(3.6)	(3.2)
Benefit costs	$ (1.2)	$ (0.2)	$ (1.4)	$ (0.2)