Employee Benefit Plans Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Pension Plan | UNITED STATES
Defined Benefit Plans and Other Postretirement Benefit Plans
Service Cost	$ 2.3	$ 2.3	$ 4.7	$ 4.6
Interest Cost	21.4	20.7	42.8	41.4
Expected Return on Plan Assets	(21.8)	(22.8)	(43.6)	(45.6)
Amortization of Net Actuarial (Gain) Loss	3.7	3.6	7.4	7.3
Amortization of Prior Service Credit			0.0	0.0
Net Periodic Benefit Cost (Credit)	5.6	3.8	11.3	7.7
Pension Plan | UNITED KINGDOM
Defined Benefit Plans and Other Postretirement Benefit Plans
Service Cost	0.0	0.0	0.0	0.0
Interest Cost	2.2	1.9	4.3	3.8
Expected Return on Plan Assets	(2.2)	(2.1)	(4.4)	(4.2)
Amortization of Net Actuarial (Gain) Loss	0.7	0.7	1.4	1.5
Amortization of Prior Service Credit			0.0	0.0
Net Periodic Benefit Cost (Credit)	0.7	0.5	1.3	1.1
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	1.0	2.0	2.0
Expected Return on Plan Assets	(0.1)	(0.1)	(0.2)	(0.2)
Amortization of Net Actuarial (Gain) Loss	(0.3)	(0.4)	(0.6)	(0.6)
Amortization of Prior Service Credit			(0.1)	(0.1)
Net Periodic Benefit Cost (Credit)	$ 0.6	$ 0.5	$ 1.1	$ 1.1