Employee Benefit Plans Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Pension Plan | UNITED STATES
Defined Benefit Plans and Other Postretirement Benefit Plans
Service Cost	$ 2.4	$ 2.8	$ 7.2	$ 8.3
Interest Cost	16.3	18.2	48.7	54.7
Expected Return on Plan Assets	(25.2)	(26.7)	(75.5)	(80.0)
Amortization of Net Actuarial Loss	5.3	4.7	16.0	14.0
Amortization of Prior Service Credit	0.0	0.0	0.0	0.0
Net Periodic Benefit Cost (Credit)	(1.2)	(1.0)	(3.6)	(3.0)
Pension Plan | UNITED KINGDOM
Defined Benefit Plans and Other Postretirement Benefit Plans
Service Cost	0.0	0.0	0.0	0.0
Interest Cost	1.1	1.3	3.2	3.7
Expected Return on Plan Assets	(2.4)	(2.4)	(7.4)	(7.1)
Amortization of Net Actuarial Loss	0.2	0.2	0.9	0.8
Amortization of Prior Service Credit	0.0	0.0	0.0	0.0
Net Periodic Benefit Cost (Credit)	(1.1)	(0.9)	(3.3)	(2.6)
Other Postretirement Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans
Service Cost	0.0	0.0	0.0	0.0
Interest Cost	0.8	1.0	2.3	3.1
Expected Return on Plan Assets	(0.1)	(0.1)	(0.4)	(0.4)
Amortization of Net Actuarial Loss	0.0	0.0	0.0	0.0
Amortization of Prior Service Credit	(0.1)	(0.1)	(0.2)	(0.2)
Net Periodic Benefit Cost (Credit)	$ 0.6	$ 0.8	$ 1.7	$ 2.5