Pension and Other Postretirement Benefits (Details) In Millions, unless otherwise specified	3 Months Ended				12 Months Ended	1 Months Ended		3 Months Ended
	Mar. 31, 2015 USD ($)	Mar. 31, 2014 USD ($)	Mar. 31, 2015 Defined Benefit Plans USD ($)	Mar. 31, 2014 Defined Benefit Plans USD ($)	Dec. 31, 2015 Defined Benefit Plans Forecast USD ($)	Jan. 30, 2015 Defined Benefit Plans United Kingdom (U.K.) USD ($)	Jan. 30, 2015 Defined Benefit Plans United Kingdom (U.K.) GBP (£)	Mar. 31, 2015 Other Postretirement Benefits USD ($)	Mar. 31, 2014 Other Postretirement Benefits USD ($)
Net periodic pension and OPEB costs:
Service cost - benefits earned during the year	$ 3.1	$ 4.0	$ 2.6	$ 3.3				$ 0.5	$ 0.7
Interest cost on projected benefit obligation	35.9	43.8	34.4	42.1				1.5	1.7
Expected return on plan assets	(44.1)	(49.1)	(44.1)	(49.1)				0	0
Amortization of prior service cost (benefit)	0.1	(0.6)	0.2	0.2				(0.1)	(0.8)
Amortization of net actuarial loss (gain)	11.2	8.9	11.2	9.1				0	(0.2)
Curtailment (gain) loss	(1.0)	0	(1.0)	0				0	0
Defined Benefit Plan Expected Participant Contributions	0.2	0.3	0.2	0.3				0	0
Net periodic pension and OPEB cost	5.0	6.7	3.1	5.3				1.9	1.4
Contributions paid to defined benefit plans	233.9					227.1	150.0
Expected total defined benefit plan employer contributions					$ 260