Employee Benefit Plans Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Plan | UNITED STATES
Defined Benefit Plans and Other Postretirement Benefit Plans
Service Cost	$ 11.0	$ 10.9	$ 9.1
Interest Cost	73.0	83.3	79.8
Expected Return on Plan Assets	(106.7)	(99.4)	(104.5)
Amortization of Net Actuarial Loss (Gain)	18.7	20.2	21.7
Amortization of Prior Service Cost (Credit)	0.1	0.0	0.0
Curtailment Gain	0.0	0.0	0.0
Net Periodic Benefit Cost	(3.9)	15.0	6.1
Pension Plan | UNITED KINGDOM
Defined Benefit Plans and Other Postretirement Benefit Plans
Service Cost	0.0	0.0	0.0
Interest Cost	4.9	6.1	5.9
Expected Return on Plan Assets	(9.5)	(8.9)	(8.9)
Amortization of Net Actuarial Loss (Gain)	1.1	0.9	0.6
Amortization of Prior Service Cost (Credit)	0.0	0.0	0.0
Curtailment Gain	0.1	0.0	0.0
Net Periodic Benefit Cost	(3.4)	(1.9)	(2.4)
Other Postretirement Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans
Service Cost	0.0	0.0	0.0
Interest Cost	4.1	5.3	4.9
Expected Return on Plan Assets	(0.5)	(0.6)	(0.6)
Amortization of Net Actuarial Loss (Gain)	0.0	(2.5)	0.0
Amortization of Prior Service Cost (Credit)	(0.2)	(0.2)	(0.2)
Curtailment Gain	0.0	0.0	0.0
Net Periodic Benefit Cost	$ 3.4	$ 2.0	$ 4.1