Pension and Other Postretirement Benefits (Details) £ in Millions, $ in Millions	1 Months Ended		3 Months Ended		6 Months Ended		12 Months Ended
	Jan. 30, 2015 GBP (£)	Jan. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Dec. 31, 2015 USD ($)
Net periodic pension and OPEB costs:
Service cost - benefits earned during the year			$ 3.0	$ 4.1	$ 6.1	$ 8.1
Interest cost on projected benefit obligation			36.4	44.5	72.3	88.3
Expected return on plan assets			(44.6)	(49.8)	(88.7)	(98.9)
Amortization of prior service cost (benefit)			0.1	(0.5)	0.2	(1.1)
Amortization of net actuarial loss (gain)			11.9	9.0	23.1	17.9
Curtailment (gain) loss					(1.0)	0.0
Defined Benefit Plan Expected Participant Contributions			(0.2)	(0.3)	(0.4)	(0.6)
Net periodic pension and OPEB cost			6.6	7.0	11.6	13.7
Contributions paid to defined benefit plans					240.2
Defined Benefit Plans
Net periodic pension and OPEB costs:
Service cost - benefits earned during the year			2.6	3.3	5.2	6.6
Interest cost on projected benefit obligation			34.9	42.6	69.3	84.7
Expected return on plan assets			(44.6)	(49.8)	(88.7)	(98.9)
Amortization of prior service cost (benefit)			0.2	0.2	0.4	0.4
Amortization of net actuarial loss (gain)			11.9	9.3	23.1	18.4
Curtailment (gain) loss					(1.0)	0.0
Defined Benefit Plan Expected Participant Contributions			(0.2)	(0.3)	(0.4)	(0.6)
Net periodic pension and OPEB cost			4.8	5.3	7.9	10.6
Defined Benefit Plans | Forecast
Net periodic pension and OPEB costs:
Expected total defined benefit plan employer contributions							$ 260.0
Defined Benefit Plans | United Kingdom (U.K.)
Net periodic pension and OPEB costs:
Contributions paid to defined benefit plans	£ 150	$ 227.1
Other Postretirement Benefits
Net periodic pension and OPEB costs:
Service cost - benefits earned during the year			0.4	0.8	0.9	1.5
Interest cost on projected benefit obligation			1.5	1.9	3.0	3.6
Expected return on plan assets			0.0	0.0	0.0	0.0
Amortization of prior service cost (benefit)			(0.1)	(0.7)	(0.2)	(1.5)
Amortization of net actuarial loss (gain)			0.0	(0.3)	0.0	(0.5)
Curtailment (gain) loss					0.0	0.0
Defined Benefit Plan Expected Participant Contributions			0.0	0.0	0.0	0.0
Net periodic pension and OPEB cost			$ 1.8	$ 1.7	$ 3.7	$ 3.1