Employee Benefit Plans Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Pension Plan | UNITED STATES
Defined Benefit Plans and Other Postretirement Benefit Plans
Service Cost	$ 2.8	$ 2.8	$ 8.3	$ 8.2
Interest Cost	18.2	20.8	54.7	62.5
Expected Return on Plan Assets	(26.7)	(24.8)	(80.0)	(74.5)
Amortization of Net Actuarial Loss	4.7	5.0	14.0	15.1
Amortization of Prior Service Cost (Credit)	0.0	0.0	0.0	0.0
Net Periodic Benefit Cost	(1.0)	3.8	(3.0)	11.3
Pension Plan | UNITED KINGDOM
Defined Benefit Plans and Other Postretirement Benefit Plans
Service Cost	0.0	0.0	0.0	0.0
Interest Cost	1.3	1.4	3.7	4.5
Expected Return on Plan Assets	(2.4)	(2.1)	(7.1)	(6.6)
Amortization of Net Actuarial Loss	0.2	0.3	0.8	0.7
Amortization of Prior Service Cost (Credit)	0.0	0.0	0.0	0.0
Net Periodic Benefit Cost	(0.9)	(0.4)	(2.6)	(1.4)
Other Postretirement Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans
Service Cost	0.0	0.0	0.0	0.0
Interest Cost	1.0	1.4	3.1	4.0
Expected Return on Plan Assets	(0.1)	(0.1)	(0.4)	(0.4)
Amortization of Net Actuarial Loss	0.0	(0.7)	0.0	(1.9)
Amortization of Prior Service Cost (Credit)	(0.1)	(0.1)	(0.2)	(0.2)
Net Periodic Benefit Cost	$ 0.8	$ 0.5	$ 2.5	$ 1.5