Employee Benefits Schedule of Net Periodic Benefit Cost and Other Comprehensive Income for Pension and Other Postretirement Benefit Plans (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Curtailment loss		$ 0
Special termination benefits		0
Settlements		0
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract]
Settlements		0
Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	2.6	3.3	4.0
Interest cost	5.3	4.8	5.1
Expected return on plan assets	(5.1)	(3.9)	(3.6)
Curtailment loss	9.3		2.2
Special termination benefits	1.9	0	0
Settlements	(0.7)	0	0
Amortization of prior service costs	4.7	5.0	5.3
Amortization of actuarial loss	0.8	2.3	1.9
Periodic expense	20.2	11.5	14.9
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract]
Current period actuarial loss (gain)	21.5	(20.8)	15.9
Amortization of actuarial loss	(0.8)	(2.3)	(1.9)
Amortization of prior service cost	(14.0)	(5.0)	(5.3)
Loss on curtailment in current period	(8.2)	0	(2.2)
Settlements	0.7	0	0
Total amount recognized in accumulated other comprehensive income	(2.2)	(28.1)	6.5
Other Postretirement Benefit Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	0	0.1	0.1
Interest cost	0.3	0.3	0.3
Expected return on plan assets	0	0	0
Curtailment loss	1.4	0	0
Special termination benefits	0	0	0
Settlements	0	0	0
Amortization of prior service costs	0.3	0.3	0.3
Amortization of actuarial loss	0	0.1	0.1
Periodic expense	2.0	0.8	0.8
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract]
Current period actuarial loss (gain)	0.6	(1.0)	0.4
Amortization of actuarial loss	0	(0.1)	(0.1)
Amortization of prior service cost	(1.7)	(0.4)	(0.4)
Loss on curtailment in current period	(0.2)	0	0
Settlements	0	0	0
Total amount recognized in accumulated other comprehensive income	$ (1.3)	$ (1.5)	$ (0.1)